BRANCHES AND LEAVES IN CONIFER. 655 
equally succeeded with Wellingtonia gigantea, and Cupressus Lawsoniana. 
Every one knows that cuttings of the common Arbor-vite root freely and grow 
into plants. Every cutting contains several ramules, which in the course of the 
season would have been cast off by the old tree. The cutting, however, takes 
root, and every ramule, instead of being cast off, developes into a true branch, 
which remains as a permanent part of the new plant. In fact, in all young 
rooted plants the change from ramules into branches goes on for several years, 
so that during that time no ramule whatever is thrown off at the end of autumn. 
The same in the case with all seedling plants. It is, in fact, only when the 
plants have attained some age and have so far acquired their full supply of 
branches, that they begin to throw offramules; but after having once begun they 
continue annually to cast them off. The same is the case with all plants raised 
from pure ramules. 
It thus appears that there is no essential difference between ramules and 
branches proper. Morphologically they are identical, save in the weaker growth 
of the former, and their ultimate fall by disarticulation; and, as regards these 
peculiarities, the foregoing experiments abundantly prove that they are of an 
adventitious or extrinsic character. 
Sub-Order ABIETINE. 
Genus Pinus.—The Pines consist of trees which in common parlance are 
termed ‘“ evergreen ”—that is to say, they remain covered with leaves both 
summer and winter. The several species, however, show great differences as to 
the period during which the leaves of a given season are retained; and this, 
when ascertained for all the species, may prove a valuable aid to botanists in 
determining alliances and ascertaining species. One great peculiarity, as is 
known, of this genus is that the green leaves or “needles” are not developed 
directly from the growing or elongating shoots, but are produced in ciusters or 
fascicles of two or more on shortened and aborted branches. The leaves of the 
growing shoots, on the other hand, are developed as chaffy scales, from whose 
axils the aborted branches with leaf-fascicles arise. When the fascicled green 
leaves are shed, they do not fall off singly, as do ordinary leaves, but in a cluster 
or mass; the aborted branchlet fallmg with them. In the genus Pinus, there- 
fore, we have a true cladoptosis analogous to that which occurs in the 
Cupressineze; but differing in that the leaves are developed on an aborted 
scarcely visible branchlet, whereas in the Cupressineze the shed ramule is fully 
developed, though its vitality may not be so strong as in those shoots which 
develope into permanent branches. 
Pinus Strobus (Weymouth Pine).—Here the leaf-fascicles of the previous 
year are thrown off in October; so that this species has two years’ growth of 
VOL XXVII. PART IV. 8K 
