CHAPTER XXXV

SUBCLASS DIPNEUSTI,[164] OR LUNGFISHES

=The Lungfishes.=--The group of Dipneusti, or lung-fishes, is characterized by the presence of paired fins consisting of a jointed axis with or without rays. The skull is autostylic, the upper jaw being made as in the Chimæra of palatal elements joined to the quadrate and fused with the cranium, without premaxillary or maxillary. The dentary bones are little developed. The air-bladder is cellular, used as a lung in all the living species, its duct attached to the ventral side of the oesophagus. The heart has many valves in the muscular arterial bulb. The intestine has a spiral valve. The teeth are usually of large plates of dentine covered with enamel, and are present on the pterygo-palatine and splenial bones. The nostrils are concealed, when the mouth is closed, under a fold of the upper lip. The scales are cycloid, mostly not enameled.

The lung-fishes, or _Dipneusti_ (~dis~, two; ~pnein~, to breathe), arise, with the Crossopterygians, from the vast darkness of Palæozoic time, their origin with that or through that of the latter to be traced to the Ichthyotomi or other primitive sharks. These two groups are separated from all the more primitive fish-like vertebrates by the presence of lungs. In its origin the lung or air-bladder arises as a diverticulum from the alimentary canal, used by the earliest fishes as a breathing-sac, the respiratory functions lost in the progress of further divergence. Nothing of the nature of lung or air-bladder is found in lancelet, lamprey, or shark. In none of the remaining groups of fishes is it wholly wanting at all stages of development, although often lost in the adult. Among fishes it is most completely functional in the _Dipneusti_, and it passes through all stages of degeneration and atrophy in the more specialized bony fishes.

In the _Dipneusti_, or Dipnoans, as in the Crossopterygians and the higher vertebrates, the trachea, or air-duct, arises, as above stated, from the ventral side of the oesophagus. In the more specialized fishes, yet to be considered, it is transferred to the dorsal side, thus avoiding a turn in passing around the oesophagus itself. From the sharks these forms are further distinguished by the presence of membrane-bones about the head. From the _Actinopteri_ (Ganoids and Teleosts) Dipnoans and Crossopterygians are again distinguished by the presence of the fringe-fin, or archipterygium, as the form of the paired limbs. From the Crossopterygians the Dipnoans are most readily distinguished by the absence of maxillary and premaxillary, the characteristic structures of the jaw of the true fish. The upper jaw in the Dipnoan is formed of palatal elements attached directly to the skull, and the lower jaw contains no true dentary bones. The skull in the Dipnoans, as in the _Chimæra_, is autostylic, the mandible articulating directly with the palatal apparatus, the front of which forms the upper jaw and of which the pterygoid, hyomandibular and quadrate elements form an immovable part. The shoulder-girdle, as in the shark, is a single cartilage, but it supports a pair of superficial membrane-bones.

In all the Dipnoans the trunk is covered with imbricated cycloid scales and no bony plates, although sometimes the scales are firm and enameled. The head has a roof of well-developed bony plates made of ossified skin and not corresponding with the membrane-bones of higher fishes. The fish-like membrane-bones, opercles, branchiostegals, etc., are not yet differentiated. The teeth have the form of grinding-plates on the pterygoid areas of the palate, being distinctly shark-like in structure. The paired fins are developed as archipterygia, often without rays, and the pelvic arch consists of a single cartilage, the two sides symmetrical and connected in front. There is but one external gill-opening leading to the gill-arches, which, as in ordinary fishes, are fringe-like, attached at one end. In the young, as with the embryo shark, there is a bushy external gill, which looks not unlike the archipterygium pectoral fin itself, although its rays are of different texture. In early forms, as in the Ganoids, the scales were bony and enameled, but in some recent forms deep sunken in the skin. The claspers have disappeared, the nostrils, as in the frog, open into the pharynx, the heart is three-chambered, the arterial bulb with many valves, and the cellular structure of the skin and of other tissues is essentially as in the Amphibian.

The developed lung, fitted for breathing air, which seems the most important of all these characters, can, of course, be traced only in the recent forms, although its existence in all others can be safely predicated. Besides the development of the lung we may notice the gradual forward movement of the shoulder-girdle, which in most of the Teleostomous fishes is attached to the head. In bony fishes generally there is no distinct neck, as the post-temporal, the highest bone of the shoulder-girdle, is articulated directly with the skull. In some specialized forms (_Balistes_, _Tetraodon_) it is even immovably fused with it. In a few groups (_Apodes_, _Opisthomi_, _Heteromi_, etc.) this connection ancestrally possessed is lost through atrophy and the slipping backward of the shoulder-girdle leaves again a distinct neck. In the Amphibians and all higher vertebrates the shoulder-girdle is distinct from the skull, and the possession of a flexible neck is an important feature of their structure. In all these higher forms the posterior limbs remain abdominal, as in the sharks and the primitive and soft-rayed fishes generally. In these the pelvis or pelvic elements are attached toward the middle of the body, giving a distinct back as well as neck. In the spiny-rayed fishes the "back" as well as the neck disappears, the pelvic elements being attached to the shoulder-girdle, and in a few extreme forms (as _Ophidion_) the pelvis is fastened at the chin.

=Classification of Dipnoans.=--By Woodward the _Dipneusti_ are divided into two classes, the _Sirenoidei_ and the _Arthrodira_. We follow Dean in regarding the latter as representative of a distinct class, leaving the _Sirenoidei_, with the _Ctenodipterini_, to constitute the subclass of _Dipneusti_. The _Sirenoidei_ are divided by Gill into two orders, the _Monopneumona_, with one lung, and the _Diplopneumona_, with the lung divided. To the latter order the _Lepidosirenidæ_ belong. To the former the _Ceratodontidæ_, and presumably the extinct families also belong, although nothing is known of their lung structures. Zittel and Hay adopt the names of _Ctenodipterini_ and _Sirenoidei_ for these orders, the former being further characterized by the very fine fin-rays, more numerous than their supports.

=Order Ctenodipterini.=--In this order the cranial roof-bones are small and numerous, and the rays of the median fins are very slender, much more numerous than their supports, which are inserted directly on the vertebral arches.

In the _Uronemidæ_ the upper dentition comprises a cluster of small, blunt, conical denticles on the palatine bones; the lower dentition consists of similar denticles on the splenial bone. The vertical fins are continuous and the tail diphycercal. There is a jugular plate, as in _Amia_. The few species are found in the Carboniferous, _Uronemus lobatus_ being the best-known species.

In _Dipteridæ_ there is a pair of dental plates on the palatines, and an opposing pair on the splenials below. Jugular plates are present, and the tail is usually distinctly heterocercal.

In _Phaneropleuron_ there is a distinct anal fin shorter than the very long dorsal; _Phaneropleuron andersoni_ is known from Scotland, and _Scaumenacia curta_ is found at Scaumenac Bay in the Upper Devonian of Canada.

In _Dipterus_ there are no marginal teeth, and the tail is heterocercal, not diphycercal, as in the other Dipnoans generally. Numerous species of _Dipterus_ occur in Devonian rocks. In these the jugular plate is present, as in _Uronemus_. _Dipterus valenciennesi_ is the best-known European species. _Dipterus nelsoni_ and numerous other species are found in the Chemung and other groups of Devonian rocks in America.

In the _Ctenodontidæ_ the tail is diphycercal, and no jugular plates are present in the known specimens. In _Ctenodus_ and _Sagenodus_ there is no jugular plate and there are no marginal teeth. The numerous species of _Ctenodus_ and _Sagenodus_ belong chiefly to the Carboniferous age. _Ctenodus wagneri_ is found in the Cleveland shale of the Ohio Devonian. _Sagenodus occidentalis_, one of the many American species, belongs to the coal-measures of Illinois.

As regards the succession of the _Dipneusti_, Dr. Dollo regards _Dipterus_ as the most primitive, _Scaumenacia_, _Uronemus_, _Ctenodus_, _Ceratodus_, _Protopterus_, and _Lepidosiren_ following in order. The last-named genus he thinks marks the terminus of the group, neither Ganoids nor Amphibians being derived from any Dipnoans.

=Order Sirenoidei.=--The living families of _Dipneusti_ differ from these extinct types in having the cranial roof-bones reduced in number. There are no jugular plates and no marginal teeth in the jaws. The tail is diphycercal in all, ending in a long point, and the body is covered with cycloid scales. To these forms the name _Sirenoidei_ was applied by Johannes Müller.

=Family Ceratodontidæ.=--The _Ceratodontidæ_ have the teeth above and below developed as triangular plates, set obliquely each with several cusps on the outer margin. Nearly all the species, representing the genera _Ceratodus_, _Gosfordia_, and _Conchopoma_, are now extinct, the single genus _Neoceratodus_ still existing in Australian rivers. Numerous fragments of _Ceratodus_ are found in Mesozoic rocks in Europe, Colorado, and India, _Ceratodus latissimus_, figured by Agassiz in 1838, being the best-known species.

The abundance of the fossil teeth of _Ceratodus_ renders the discovery of a living representative of the same type a matter of great interest.

In 1870 the Barramunda of the rivers of Queensland was described by Krefft, who recognized its relationship to _Ceratodus_ and gave it the name of _Ceratodus forsteri_. Later, generic differences were noticed, and it was separated as a distinct group by Castelnau in 1876, under the name of _Neoceratodus_ (later called _Epiceratodus_ by Teller). _Neoceratodus forsteri_ and a second species, _Neoceratodus miolepis_, have been since very fully discussed by Dr. Günther and Dr. Krefft. They are known in Queensland as _Barramunda_. They inhabit the rivers known as Burnett, Dawson, and Mary, reaching a length of six feet, and being locally much valued as food. From the salmon-colored flesh, they are known to the settlers in Queensland as "salmon." According to Dr. Günther, "the Barramunda is said to be in the habit of going on land, or at least on mud-flats; and this assertion appears to be borne out by the fact that it is provided with a lung. However, it is much more probable that it rises now and then to the surface of the water in order to fill its lung with air, and then descends again until the air is so much deoxygenized as to render a renewal of it necessary. It is also said to make a grunting noise which may be heard at night for some distance. This noise is probably produced by the passage of the air through the oesophagus when it is expelled for the purpose of renewal. As the Barramunda has perfectly developed gills besides the lung, we can hardly doubt that, when it is in water of normal composition and sufficiently pure to yield the necessary supply of oxygen, these organs are sufficient for the purpose of breathing, and that the respiratory function rests with them alone. But when the fish is compelled to sojourn in thick muddy water charged with gases, which are the products of decomposing organic matter (and this must be the case very frequently during the droughts which annually exhaust the creeks of tropical Australia), it commences to breathe air with its lung in the way indicated above. If the medium in which it happens to be is perfectly unfit for breathing, the gills cease to have any function; if only in a less degree, the gills may still continue to assist in respiration. The Barramunda, in fact, can breathe by either gills or lung alone or by both simultaneously. It is not probable that it lives freely out of water, its limbs being much too flexible for supporting the heavy and unwieldy body and too feeble generally to be of much use in locomotion on land. However, it is quite possible that it is occasionally compelled to leave the water, although we cannot believe that it can exist without it in a lively condition for any length of time.

"Of its propagation or development we know nothing except that it deposits a great number of eggs of the size of those of a newt, and enveloped in a gelatinous case. We may infer that the young are provided with external gills, as in _Protopterus_ and _Polypterus_.

"The discovery of _Ceratodus_ does not date farther back than the year 1870, and proved to be of the greatest interest, not only on account of the relation of this creature to the other living _Dipneusti_ and _Ganoidei_, but also because it threw fresh light on those singular fossil teeth which are found in strata of Triassic and Jurassic formations in various parts of Europe, India, and America. These teeth, of which there is a great variety with regard to general shape and size, are sometimes two inches long, much longer than broad, depressed, with a flat or slightly undulated, always punctated, crown, with one margin convex, and with from three to seven prongs projecting on the opposite margin."

=Development of Neoceratodus.=--From DEAN'S "Fishes, Recent and Fossil," pp. 218-221, we condense the following account (after the observations of Dr. F. Semon) of the larval history of the Barramunda, _Neoceratodus forsteri_:

It offers characters of exceptional interest, uniting features of Ganoids with those of Cyclostomes and Amphibians.

The newly hatched _Neoceratodus_ does not strikingly resemble the early larva of shark. No yolk-sac occurs, and the distribution of the yolk material in the ventral and especially the hinder ventral region is suggestive rather of lamprey or amphibian; it is, in fact, as though the quantum of yolk material had been so reduced that the body form had not been constricted off from it. The caudal tip in this stage appears, however, to resemble that of the shark, and, as far as can be inferred from surface views, a neurenteric canal persists. Like the shark there then exists no unpaired fin; the gill-slits (five?) are well separated and there is an abrupt cephalic flexure. In this stage pronephros (primitive kidney) and primitive segments are well marked, and are outwardly similar to those structures in Ganoid; the mouth is on the point of forming its connection with the digestive cavity; the anus is the persistent blastophore; the heart, well established, takes a position, as in Cyclostomes, immediately in front of the yolk material.

In a later stage the unpaired fin has become perfectly established, the tail increasing in length; the gill-slits have now been almost entirely concealed by a surrounding dermal outgrowth, the embryonic operculum; a trace of the pectoral fin appears; the lateral line is seen proceeding down the side of the body; near the anal region the intestine[165] becomes narrower, and the beginnings of the spiral valve appear. In a larva of two weeks a number of developmental advances are noticed; the fish has become opaque; the primitive segments are no longer seen; the size of the yolk mass is reduced; the anal fin-fold appears; sensory canals are prominent in the head region; lateral line is completely established; the rectum becomes narrowed; and the cycloidal body-scales are already outlined. Gill-filaments may still be seen beyond the rim of the outgrowing operculum. In the ventral view of a somewhat later larva the following structures are to be noted: the pectoral fins, which have now suddenly budded out,[166] reminding one in their late appearance of the mode of origin of the anterior extremity of urodele; the greatly enlarged size of the opercular flap; external gills, still prominent; the internal nares, becoming constricted off into the mouth-cavity by the dermal fold of the anterior lip (as in some sharks); and finally (as in _Protopterus_ and some batrachian larvæ) the one-sided position of the anus.

The larva of six weeks suggests the outline of the mature fish; head and sides show the various openings of the tubules of the insunken sensory canals; and the archipterygium of the pectoral fin is well defined. The oldest larva figured is ten weeks old; its operculum and pectoral fin show an increased size; the tubular mucous openings, becoming finely subdivided, are no longer noticeable; and although the basal supports of the remaining fins are coming to be established, there is as yet little more than a trace of the ventrals.

The early development of a lung-fish has thus far been described (Semon) only from the outward appearance of the embryo. The egg of _Neoceratodus_ has its upper pole distinguished by its fine covering of pigment. From the first fine planes of cleavage it will be seen that the yolk material of the lower pole is not sufficient to prevent the egg's total segmentation. The first plane of cleavage is a vertical one, passing down the side of the egg as a shallow surface furrow, not appearing to entirely separate the substance of the blastomeres, although traversing completely the lower hemisphere. A second vertical furrow at right angles to the first is seen from the upper pole. The third cleavage is again a vertical one (as in all other fishes, but unlike _Petromyzon_), approximately meridional; its furrows appear less clearly marked than those of earlier cleavages, and seem somewhat irregular in occurrence. The fourth cleavage is horizontal above the plane of the equator. Judging from Semon's figure, at this stage the furrows of the lower pole seem to have become fainter, if not entirely lost. In a blastula showing complete segmentation the blastomeres of the upper hemisphere are the more finely subdivided. In the earlier stage the dorsal lip of the blastopore is crescent-like; in the later the blastopore acquires its oblong outline, through which the yolk material is apparent; its conditions may later be compared to those of a Ganoid.

The next change of the embryo is strikingly amphibian-like; the medullary folds rise above the egg's surface, and, arching over, fuse their edges in the median dorsal line. The medullary folds are seen closely apposed in the median line; hindward, however, they are still separate, and through this opening the blastopore may yet be seen. At this stage primitive segments are shown; in the brain region the medullary folds are still slightly separated.

In an older embryo the fish-like form may be recognized. The medullary folds have completely fused in the median line, and the embryo is coming to acquire a ridge-like prominence; optic vesicles and primitive segments are apparent, and the blastopore appears to persist as the anus. The continued growth of the embryo above the yolk mass is apparent; the head end has, however, grown the more rapidly, showing gill-slits, auditory, optic, and nasal vesicles, at a time when the tail mass has hardly emerged from the surface. Pronephros has here appeared. It is not until the stage of the late embryo that the hinder trunk region and tail come to be prominent. The embryo's axis elongates and becomes straighter; the yolk mass is now much reduced, acquiring a more and more oblong form, lying in front of the tail in the region of the posterior gut. The head and even the region of the _pronephros_ are clearly separate from the yolk-sac; the mouth is coming to be formed.

According to Eastman (Ed. Zittel), the skeleton of _Neoceratodus_ is less developed and less ossified than that of its supposed Triassic ancestors. A similar rule holds with regard to the sturgeons and some Amphibians.

=Lepidosirenidæ.=--The family _Lepidosirenidæ_, representing the suborder _Diplopneumona_, is represented by two genera of mudfishes found in streams of Africa and South America. _Lepidosiren paradoxa_ was discovered by Natterer in 1837 in tributaries of the Amazon. It was long of great rarity in collections, but quite recently large numbers have been obtained, and Dr. J. Graham Kerr of the University of Cambridge has given a very useful account of its structure and development. From his memoir we condense the following record of its habits as seen in the swamps in a region known as Gran Chaco, which lies under the Tropic of Capricorn. These swamps in the rainy season have a depth of from two to four feet, becoming entirely dry in the southern winter (June, July).

=Kerr on the Habits of Lepidosiren.=--The loalach, as the _Lepidosiren_ is locally called, is normally sluggish, wriggling slowly about at the bottom of the swamp, using its hind limbs in irregular alternation as it clambers through the dense vegetation. More rapid movement is brought about by lateral strokes of the large and powerful posterior end of the body. It burrows with great facility, gliding through the mud, for which form of movement the shape of the head, with the upper lip overlapping the lower and the external nostril placed within the lower lip, is admirably adapted. It feeds on plants, algæ, and leaves of flower-plants. The gills are small and quite unable to supply its respiratory needs, and the animal must rise to the surface at intervals, like a frog. It breathes with its lungs as continuously and rhythmically as a mammal, the air being inhaled through the mouth. The animal makes no vocal sound, the older observation that it utters a cry like that of a cat being doubtless erroneous. Its strongest sense is that of smell. In darkness it grows paler in color, the black chromatophores shrinking in absence of light and enlarging in the sunshine. In injured animals this reaction becomes much less, as they remain pale even in daylight.

In the rainy season when food is abundant the Lepidosiren eats voraciously and stores great quantities of orange-colored fat in the tissues between the muscles. In the dry season it ceases to feed, or, as the Indians put it, it feeds on water. When the water disappears the Lepidosiren burrows down into the mud, closing its gill-openings, but breathing through the mouth. As the mud stiffens it retreats to the lower part of its burrow, where it lies with its tail folded over its face, the body surrounded by a mucous secretion. In its burrow there remains an opening which is closed by a lid of mud. At the end of the dry season this lid is pushed aside, and the animal comes out when the water is deep enough. When the waters rise the presence of Lepidosirens can be found only by a faint quivering movement of the grass in the bottom of the swamp. When taken the body is found to be as slippery as an eel and as muscular. The eggs are laid in underground burrows in the black peat. Their galleries run horizontally and are usually two feet long by eight inches wide. After the eggs are laid the male remains curled up in the nest with them. In the spawning season an elaborate brush is developed in connection with the ventral fins.

_Protopterus_, a second genus, is found in the rivers of Africa, where three species, _P. annectens_, _P. dolloi_, and _P. æthiopicus_, are now known.

The genus has five gill-clefts, instead of four as in _Lepidosiren_. It retains its external gills rather longer than the latter, and its limbs are better developed. The habits of _Protopterus_ are essentially like those of _Lepidosiren_, and the two types have developed along parallel lines doubtless from a common ancestry. No fossil _Lepidosirenidæ_ are known.

Just as the last page of this volume passes through the press, there has appeared a bold and striking memoir on the "Phylogeny of the Teleostomi," by Mr. C. Tate Regan of the British Museum of Natural History. In this paper Mr. Regan takes the view that the Chondrostean Ganoids (_Palæoniscum_, _Chondrosteus_, _Polyodon_, _Psephurus_, etc.) are the most primitive of the Teleostomous fishes; that the _Crossopterygii_, the _Dipneusti_, the _Placodermi_, and the _Teleostei_ (as well as the higher vertebrates) are descended from these; that the _Coccosteidæ_ (Arthrodires) are the most generalized of the Placoderms, the _Osteostraci_ and most of the other forms called Ostracophores (_Antiarcha_, _Anaspida_) being allied to the Arthrodires, and to be included with them among the _Placodermi_; that the cephalic appendage of _Pterichthyodes_, etc., is really a pectoral fin; that the _Heterostraci_ (_Lanarkia_, _Pteraspis_, etc.) are not Ostracophores or Placoderms at all, but mailed primitive sharks, derived from the early sharks as the Chimæras are, and that the Holostean Ganoids (_Lepisosteus_, _Amia_, etc.) should be separated from the _Chondrostei_ and referred to the _Teleostei_, of which they are the primitive representatives.

Mr. Regan especially calls attention to the very close similarity in structure of pectoral and ventral fins in the Chondrostean Ganoids, _Psephurus_ and _Polyodon_, with that of the anal fin in the same fishes. From this he derives additional evidence in favor of the origin of paired fins from a lateral fold. In his view, the _Chondrostei_ have sprung directly, through ancestors of the _Lysopteri_ and _Selachostomi_, from pleuropterygian sharks (_Cladoselache_) of the Lower Silurian, and the true fishes on the one hand and the Crossopterygian-Dipneustan-Placoderm series on the other are descended from these. The absence of the lower jaw in fossil remains of Ostracophores may be due to its cartilaginous structure. "There is no justification for regarding the _Crossopterygii_ as less specialized than the _Chondrostei_ because they were the earlier dominant group."

These views are very suggestive and contain at least some elements of taxonomic advance, although few naturalists of to-day will regard the Chondrostean Ganoids as more primitive than the fishes called _Crossopterygii_ and _Placoderms_.

These conclusions are summarized by Mr. Regan as follows:

(1) The _Chondrostei_ are the most generalized _Teleostomi_.

(2) The _Crossopterygii_ differ from them

(_a_) in the lobate pectoral fin;

(_b_) in the larger paired gular plates.

(3) The _Placodermi_ (_Coccosteidæ_, _Asterolepidæ_, _Cephalaspidæ_) are a natural group, not related to the _Heterostraci_, which are _Chondropterygii_. They may probably be regarded as armored _primitive Crossopterygii_, this view being most in accordance with

(_a_) the arrangement of the cranial roof-bones in _Coccosteus_;

(_b_) the structure of the ventral fin in _Coccosteus_;

(_c_) the structure of the pectoral limb of the _Asterolepidæ_.

(4) The _Dipneusti_ probably originated from more specialized _Crossopterygii_, e.g., from the neighborhood of the _Holoptychiidæ_.

(5) The Teleostei differ in so many respects from the _Chondrostei_ that they should rank as an order, in which the _Holostei_ are included.

FOOTNOTES:

[164] This group has been usually known as _Dipnoi_, a name chosen by Johannes Müller in 1845. But the latter term was first taken by Leuckart in 1821 as a name for Amphibians before any of the living _Dipneusti_ were known. We therefore follow Boulenger in the use of the name _Dipneusti_, suggested by Hæckel in 1866. The name Dipnoan may, however, be retained as a vernacular equivalent of _Dipneusti_.

[165] The yolk appears to be contained in the digestive cavity, as in _Ichthyophis_ and lamprey.

[166] The abbreviated mode of development of the fins is most interesting; from the earliest stage they assume outwardly the archipterygial form; the retarded development of the limbs seems curiously amphibian-like; the pectorals do not properly appear until about the third week, the ventrals not until after the tenth.

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FERNS

A MANUAL FOR THE NORTHEASTERN STATES WITH ANALYTICAL KEYS BASED ON THE STALKS AND ON THE FRUCTIFICATION

_With over two hundred illustrations from original drawings and photographs_

BY CAMPBELL E. WATERS

302 pages, square 8vo. Boxed, $3.00 net; by mail, $3.34

This book is thoroughly authoritative, and is written in popular style. It covers all the ferns in the region embraced either in Britton's or in Gray's Manuals.

"This book is likely to prove the leading popular work on ferns. =No finer examples of fern photography have ever been produced.= Dr. Waters brings to his work fifteen years of experience in field and herbarium study, and the book may be expected to prove of permanent scientific value, as well as to satisfy a want which existing treatises have but imperfectly filled."--_Plant World._

"For all who study or wish to study our native ferns Dr. Waters has prepared a book which is sure to prove =both helpful and inspiring=. Especially charming and significant are the views showing typical habits and habitats."--_The American Naturalist._

"There could hardly be a better book for those interested in the subject."--_Boston Literary World._

OUR NATIVE FERNS

AND THEIR ALLIES

_WITH SYNOPTICAL DESCRIPTION OF THE AMERICAN PTERIDOPHYTA NORTH OF MEXICO_

BY LUCIEN M. UNDERWOOD

PROFESSOR IN COLUMBIA UNIVERSITY

Revised. xii+156 pages, 12mo $1.00

"The elementary part is clear and well calculated to introduce beginners to the study of the plants treated of. The excellent key makes the analysis of ferns comparatively easy. The writer cordially commends the book. It should be in the hands of all who are especially interested in the vascular cryptogams of the United States."--_Bulletin of the Torrey Botanical Club, N. Y._

Henry Holt and Company

29 West 23d Street, New York

MUSHROOMS

BY GEORGE FRANCIS ATKINSON

_Professor of Botany in Cornell University, and Botanist of the Cornell University Experiment Station_

=Recipes for Cooking Mushrooms.= By MRS. SARAH TYSON RORER

=Chemistry and Toxicology of Mushrooms.= By J. F. CLARK

_With 230 illustrations from photographs, including 15 colored plates_

320 pages, 8vo. $3.00 net; by mail, $3.23

_Educational Review_:--"It would be difficult to conceive of a more attractive and useful book.... In addition to its general attractiveness and the beauty of its illustrations, it is written in a style well calculated to win the merest tyro."

Moulds, Mildews, and Mushrooms

BY LUCIEN M. UNDERWOOD

_Professor in Columbia University_

iv+236 pages, 12mo $1.50

_Bradley M. Davis_, in the BOTANICAL GAZETTE:--"Wonderfully free from the dry diagnoses of most systematic descriptions, and everywhere combined with interesting accounts of life-habits and activities.... A marvel in its compactness, with a wonderfully uniform tone throughout, condensed and yet very clear."

Flora of the Northern States and Canada

BY PROFESSOR N. L. BRITTON

_Director of the New York Botanical Garden_

x+1080 pages, large 12mo $2.25

This manual is published in response to a demand for a handbook suitable for ordinary school use, which shall meet modern requirements and outline modern conceptions of the science. It is based on _An Illustrated Flora_ prepared by Professor Britton in co-operation with Judge Addison Brown, in three volumes. The text has been revised and brought up to date, and much of novelty has been added, but all illustrations are omitted.

CONWAY MACMILLAN, _Professor in the University of Minnesota_, in SCIENCE:--"There is no work extant in the whole series of American botanical publications which deals with descriptions of the flowering plants that can for a moment be compared with it, either for a skillful and delightful presentation of the subject-matter or for modern, scientific, and accurate mastery of the thousandfold mass of detail of which such a work must consist."

V. M. SPALDING, _Professor in the University of Michigan_:--"I regard the book as one that we cannot do without and one that will henceforth take its place as a necessary means of determination of the plant species within its range."

Henry Holt and Company

29 West 23d Street, New York

Transcriber's Notes:

Simple spelling, grammar, and typographical errors were corrected.

Punctuation normalized.

Anachronistic and non-standard spellings retained as printed.

The ERRATA on p. ix has been corrected in the text.

P. xxiii corrected "_Salmo gairdneri_, the Steelhead Trout. 326" to "_Salmo irideus_, the Rainbow Trout. 326" to agree with the actual illustration caption.

P. xxiii corrected "_Salmo rivularis_, the Steelhead Trout. 327" to "_Salmo gairdneri_, the Steelhead Trout. 327" to agree with the actual illustration caption.

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