Chapter 42

PERSISTENCE OF JUVENILE FORMS.

The retention in adult life of a form characteristic of an early stage of development, and therefore usually transient, may be manifested in any of the organs of the plant. As these cases are for the most part treated under separate headings, it is here only necessary to allude to a few, which it is difficult to allocate satisfactorily, while the reader may be referred for other instances of like nature to the sections on Peloria, Atrophy, Suppression, Dimorphy, Substitutions, &c.

=Stasimorphy in the leaves of conifers.=--In many conifers the leaves produced in the young state of the plant are different, both in arrangement and form, from those subsequently developed (see pp. 89, 90). But it occasionally happens that the plant continues to form throughout its existence leaves such as are usually produced only in a young state; thus M. Gubler ('Bull. Soc. Bot., Fr.,' vol. viii, 1861, p. 527) describes a plant of _Pinus pinea_ in which the primordial, usually transitory, foliage was permanent, leaves of the ordinary shape not being developed at all. It more often happens that some only of the leaves retain their young form while others assume other shapes, see fig. 115. This happens frequently in the larch and constantly in the Chinese juniper when it has arrived at a considerable age. In _Cupressus funebris_ two forms of leaves may often be found on the same plant, the one representing the juvenile state, the other the more developed condition. What is very singular, is that a cutting taken from the branch with leaves of the young form grows up into a shrub bearing leaves of no other shape, so that an ordinary observer unacquainted with the history of the plant would imagine that he had to deal with two distinct species. This fact is the more interesting when compared with the alternation of generations which takes place among the lower animals.

The regular development of all the parts of the flower in a plant habitually producing irregular flowers is referred to under the head of Peloria, but it still remains to consider those examples in which some only of the parts of the flower are affected in this manner.[220] Most of these cases are elsewhere referred to in this volume under the particular form of malformation assumed; but the following case may here be noticed as not coming under any of the previous heads. It is an instance recorded by Professor Babington ('Phytologist,' August, 1853), and in which the pod of _Medicago maculata_, which is usually rolled up like a snail shell and provided with spines, was sickle-shaped and unarmed.

FOOTNOTES:

[220] See a paper of Professor C. Morren's on "Floral Stesomy" in 'Bull. Acad. Belg.,' t. xix, part ii, p. 519.