Chapter 9

We now come to the animal life in mines and pits. This is mostly represented, of course, by lower organisms, as infusoria and worms. Thus, in the slime on the bottom of the waters in mines, several species of _amoebæ_ are found, which consist of microscopically small animated bodies, continually floating about, nourishing themselves by absorbing organic matter, possessing sensation, propagating, etc., and, in fact, having actually the qualities of real animal nature. Further, we find in those subterraneous waters a species of the sun infusorium (_Actinophrys_), which is especially frequent in the mines of Klausthal. Fig. 6 shows one of these peculiar little beings. Also the _Stylonychia_ (Fig. 7) is a characteristic inhabitant of those places, and always present there.

It moves with great rapidity in the water by means of the numerous hairs covering its body, can turn quickly in any direction, and thus is enabled to catch suddenly the little beings on which it lives and which it hunts; for which reason the stylonychia is called the "rapacious infusorium."

The above are organisms which can be seen only through the microscope, but the fauna of mines contains also larger organisms, though they are not found as regularly and are not as characteristic for those places as the forms mentioned hitherto. Among these organisms there are several species of worms, spiders, gnats, and, above all, crustaceans of the lower class. The most interesting of the latter is perhaps a variety of the sand flea (Fig. 8--_Gammarus pulex_). The crustacean found in the pits of mines, which is related to the sand flea, shows, according to Dr. R. Schneider, a slight degeneration of the organ of sight, which has taken place in consequence of its adaptation to the dark places, in which this variety of the _Gammarus pulex_ is found, which can make no use of eyes, while the sand flea possesses them fully developed. Otherwise, however, the two varieties are almost absolutely alike, differing only in some details.

From the above the reader will see that "breathing in the rosy light," as Schiller calls it, is not an absolutely necessary condition for the existence of organic beings, but that life exists everywhere, where there is air and moisture, and a temperature which is not always below freezing point, though even eternal frost does not exclude life entirely, as is proved by the existence of the glacier flea, showing that even in the icy coverings of the Alps life still is possible. Mephistopheles may therefore well say:

"From water, earth, and air unfolding, A thousand germs break forth and grow In dry and wet, and warm and chilly; And had I not the Flame reserved, why really, There's nothing special of my own to show!"

--_Leipziger Illustrirte Zeitung._

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[NATURE.]

TIMBER, AND SOME OF ITS DISEASES.[1]

[Footnote 1: Continued from Supplement, No. 661, page 10558.]

By H. MARSHALL WARD.

IX.

In the months of April and May, the younger needle-like leaves of the Scotch pine are occasionally seen to have assumed a yellow tinge, and on closer examination this change in color, from green to yellow, is seen to be due to the development of what look like small orange colored vesicles standing off from the surface of the epidermis, and which have in fact burst through from the interior of the leaf (Fig. 31). Between these larger orange yellow vesicles the lens shows certain smaller brownish or almost black specks. Each of the vesicular swellings is a form of fungus fructification known as an _Æcidium_, and each of the smaller specks is a fungus structure called a _Spermogonium_, and both of these bodies are developed from a mycelium in the tissues of the leaf. I must employ these technical terms, but will explain them more in detail shortly: the point to be attended to for the moment is that this fungus in the leaf has long been known under the name of _Peridermium Pini_ (var. _acicola_, i.e., the variety which lives upon the needle-like leaves).

On the younger branches of the Scotch pine, the Weymouth pine, the Austrian pine, and some others, there may also be seen in May and June similar but larger bladder-like orange vesicles (_Æcidia_) bursting through the cortex (Fig. 31); and here, again, careful examination shows the darker smaller _Spermogonia_ in patches between the _Æcidia_. These also arise from a fungus mycelium in the tissues of the cortex, whence the fungus was named _Peridermium Pini_ (var. _corticola_). It is thus seen that the fungus _Peridermium Pini_ was regarded as a parasite of pines, and that it possessed two varieties, one inhabiting the leaves and the other the cortex: the "varieties" were so considered, because certain trivial differences were found in the minute structure of the _Æcidia_ and _Spermogonia_.

If we cut thin vertical sections through a leaf and one of the smallest _Æcidia_, and examine the latter with the microscope, it will be found to consist of a mass of spores arranged in vertical rows, each row springing from a branch of the mycelium: the outermost of these spores--i.e., those which form a compact layer close beneath the epidermis--remain barren, and serve as a kind of membrane covering the rest (Fig. 33, p). It is this membrane which protrudes like a blister from the tissues. The hyphæ of the fungus are seen running in all directions between the cells of the leaf tissue, and as they rise up and form the vertical chains of spores, the pressure gradually forces up the epidermis of the leaf, bursts it, and the mass of orange yellow powdery spores protrude to the exterior enveloped in the aforesaid membrane of contiguous barren spores. If we examine older _Æcidia_, it will be found that this membrane bursts also at length, and the spores escape.

Similar sections across a _Spermogonium_ exhibit a structure which differs slightly from the above. Here also the hyphæ in the leaf turn upward, and send delicate branches in a converging crowd beneath the epidermis; the latter gives way beneath the pressure, and the free tips of the hyphæ constrict off very minute spore-like bodies. These minute bodies are termed _Spermatia_, and I shall say no more about them after remarking that they are quite barren, and that similar sterile bodies are known to occur in very many of the fungi belonging to this and other groups.

Sections through the _Æcidia_ and _Spermogonia_ on the cortex present structures so similar, except in minute details which could only be explained by lengthy descriptions and many illustrations, that I shall not dwell upon them; simply reminding the reader that the resemblances are so striking that systematic mycologists have long referred them to a mere variety of the same fungus.

Now as to the kind and amount of damage caused by the ravages of these two forms of fungus.

In the leaves, the mycelium is found running between the cells (Fig. 33, h), and absorbing or destroying their contents: since the leaves do not fail the first season, and the mycelium remains living in their tissues well into the second year, it is generally accepted that it does very little harm. At the same time, it is evident that, if very many leaves are being thus taxed by the fungus, they cannot be supplying the tree with food materials in such quantities as if the leaves were intact. However, the fungus is remarkable in this respect--that it lives and grows for a year or two in the leaves, and does not (as so many of its allies do) kill them after a few weeks. It is also stated that only young pines are badly attacked by this form: it is rare to find _Æcidia_ on trees more than twenty years or so old.

Much more disastrous results can be traced directly to the action of the mycelium in the cortex. The hyphæ grow and branch between the green cells of the true cortex, as well as in the vast tissues beneath, and even make their way into the medullary rays and resin canals in the wood, though not very deep. Short branches of the hyphæ pierce the cells, and consume their starch and other contents, causing a large outflow of resin, which soaks into the wood or exudes from the bark. It is probable that this effusion of turpentine into the tissues of the wood, cambium, and cortex has much to do with the drying up of the parts above the attacked portion of the stem: the tissues shrivel up and die, the turpentine in the canals slowly sinking down into the injured region. The drying up would of course occur if the conducting portions are steeped in turpentine, preventing the conduction of water from below.

The mycelium lives for years in the cortex, and may be found killing the young tissues just formed from the cambium during the early summer: of course the annual ring of wood, etc., is here impoverished. If the mycelium is confined to one side of the stem, a flat or depressed spreading wound arises; if this extends all round, the parts above must die.

When fairly thick stems or branches have the mycelium on one side only, the cambium is injured locally, and the thickening is of course partial. The annual rings are formed as usual on the opposite side of the stem, where the cambium is still intact, or they are even thicker than usual, because the cambium there diverts to itself more than the usual share of food substances; where the mycelium exists, however, the cambium is destroyed, and no thickening layer is formed. From this cause arise cancerous malformations which are very common in pine woods (Fig. 34).

Putting everything together, it is not difficult to explain the symptoms of the disease. The struggle between the mycelium on the one hand, which tries to extend all round in the cortex, and the tree itself, on the other, as it tries to repair the mischief, will end in the triumph of the fungus as soon as its ravages extend so far as to cut off the water supply to the parts above: this will occur as soon as the mycelium extends all round the cortex, or even sooner if the effusion of turpentine hastens the blocking up of the channels. This may take many years to accomplish.

So far, and taking into account the enormous spread of this disastrous disease, the obvious remedial measures seem to be, to cut down the diseased trees--of course this should be done in the winter, or at least before the spores come--and use the timber as best may be; but we must first see whether such a suggestion needs modifying, after learning more about the fungus and its habits. It appears clear, at any rate, however, that every diseased tree removed means a source of Æcidiospores the less. Probably every one knows the common groundsel, which abounds all over Britain and the Continent, and no doubt many of my readers are acquainted with other species of the same genus (_Senecio_) to which the groundsel belongs, and especially with the ragwort (_Senecio Jacobæa_). It has long been known that the leaves of these plants, and of several allied species, are attacked by a fungus, the mycelium of which spreads in the leaf passages, and gives rise to powdery masses of orange yellow spores, arranged in vertical rows beneath the stomata: these powdery masses of spores burst forth through the epidermis, but are not clothed by any covering, such as the _Æcidia_ of _Peridermium Pini_, for instance. These groups of yellow spores burst forth in irregular powdery patches, scattered over the under sides of the leaves in July and August: toward the end of the summer a slightly different form of spore, but similarly arranged, springs from the same mycelium on the same patches. From the differences in their form, time of appearance, and (as we shall see) functions, these two kinds of spores have received different names. Those first produced have numerous papillæ on them, and were called _Uredospores_, from their analogies with the uredospore of the rust of wheat; the second kind of spore is smooth, and is called the _Teleutospore_, also from analogies with the spores produced in the late summer by the wheat rust. The fungus which produces these uredospores and teleutospores was named and has been long distinguished as _Coleosporium Senecionis_ (Pers.) We are not immediately interested in the damage done by this parasite to the weeds which it infests, and at any rate we might well be tempted to rejoice in its destructive action on these garden pests. It is sufficient to point out that the influence of the mycelium is to shorten the lives of the leaves, and to rob the plant of food material in the way referred to generally in my last article.

What we are here more directly interested in is the following. A few years ago Wolff showed that if the spores from the _Æcidia Peridermium Pini_ (var. _acicola_) are sown on the leaf of _Senecio_, the germinal hyphæ which grow out from the spores _enter the stomata of the Senecio leaf, and there develop into the fungus called Coleosporium Senecionis_. In other words, the fungus growing in the cortex of the pine, and that parasitic on the leaves of the groundsel and its allies, are one and the same: it spends part of its life on the tree and the other part on the herb.

If I left the matter stated only in this bald manner, it is probable that few of my readers would believe the wonder. But, as a matter of fact, this phenomenon, on the one hand, is by no means a solitary instance, for we know many of these fungi which require two host plants in order to complete their life history; and, on the other hand, several observers of the highest rank have repeated Wolff's experiment and found his results correct. Hartig, for instance, to whose indefatigable and ingenious researches we owe most that is known of the disease caused by the _Peridermium_, has confirmed Wolff's results.

It was to the brilliant researches of the late Prof. De Bary that we owe the first recognition of this remarkable phenomenon of _heteroecism_--i.e., the inhabiting more than one host--of the fungi. De Bary proved that the old idea of the farmer, that the rust is very apt to appear on wheat growing in the neighborhood of berberry bushes, was no fable; but on the contrary, that the yellow _Æcidium_ on the berberry is a phase in the life history of the fungus causing the wheat rust. Many other cases are now known, e.g.., the _Æcidium abietinum_, on the spruce firs in the Alps, passes the other part of its life on the rhododendrons of the same region. Another well known example is that of the fungus _Gymnosporangium_, which injures the wood of junipers. Oersted first proved that the other part of its life is spent on the leaves of certain Rosaceæ, and his discovery has been repeatedly confirmed. I have myself observed the following confirmation of this. The stems of the junipers so common in the neighborhood of Silverdale (near Morecambe Bay) used to be distorted with _Gymnosporangium_, and covered with the _teleutospores_ of this fungus every spring: in July all the hawthorn hedges in the neighborhood had their leaves covered with the Æcidium form (formerly called Roestelia), and it was quite easy to show that the fungus on the hawthorn leaves was produced by sowing the _Gymnosporangium_ spores on them. Many other well established cases of similar heteroecism could be quoted.

But we must return to the _Peridermium Pini_. It will be remembered that I expressed myself somewhat cautiously regarding the _Peridermium_ on the leaves (var. _acicola_). It appears that there is need for further investigations into the life history of this form, for it has been thought more than probable that it is not a mere variety of the other, but a totally different species.

Only so lately as 1883, however, Wolff succeeded in infecting the leaves of _Senecio_ with the spores of _Peridermium Pini_ (_acicola_), and developing the _Coleosporium_, thus showing that both the varieties belong to the same fungus.

It will be seen from the foregoing that in the study of the biological relationships between any one plant which we happen to value because it produces timber and any other which grows in the neighborhood there may be (and there usually is) a series of problems fraught with interest so deep scientifically, and so important economically, that one would suppose no efforts would be spared to investigate them: no doubt it will be seen as time progresses that what occasionally looks like apathy with regard to these matters is in reality only apparent indifference due to want of information.

Returning once more to the particular case in question, it is obvious that our new knowledge points to the desirability of keeping the seed beds and nurseries especially clean from groundsel and weeds of that description: on the one hand, such weeds are noxious in themselves, and on the other they harbor the _Coleosporium_ form of the fungus _Peridermium_ under the best conditions for infection. It may be added that it is known that the fungus can go on being reproduced by the _uredospores_ on the groundsel plants which live through the winter.

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In St. Genevieve and Cape Girardeau Counties, Mo., in the Niagara limestone is found a handsome marble of a variegated liver color. Near Sheppard Landing it is 80 feet thick, and at Janis Mill, in St. Genevieve County, Dr. Shumard speaks of beds of fine texture and various shades of flesh, yellow, green, pink, purple, and chocolate, all handsomely blended.

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