70 A. H. Graves, 
fig. 36). In the case of the stem, however, the natural arrangement 
often remains apparent (Pl. I, fig. 2; Pl. Il, fig. 6). 
On account of this distichous system, it is possible to cut a 
longitudinal section through all of the branches and the stem at 
the same time, especially if the region of the growing point is 
selected, ‘as’ is represented im Plid, fig.e1 (ch Pl) Viliiese2a): 
* A study of this figure of a vigorously developing stem apex will 
show clearly the order of development and the orientation of the 
branches. Since the origin of the branches is inseparably connected 
with the leaf development, it will be necessary to include in a 
description of the figure some reference to leaf development. 
The apical growing point G P has given off in alternate succession 
the primary leaves L4 LY, Li, L1V, &c. A secondary growing 
point arises in the axil of each of these leaves, which develops 
leaves in the same manner. The first leaf, however, is a scale leaf, 
which will be discussed at length later. (See p. 99.) 
Since L4 LU, LI, LIV, &c. are developed in acropetal suc- 
cession and hence show equal gradations in age, a study of their 
successive axillary structures presents a clear idea of the manner 
of development of the branch. The youngest leaves, LV! and 
LVI are hardly more than protuberances from opposite sides of 
the growing point, and as yet reveal no structures in their axils. 
At L YI we first see a small axillary growing point—the beginning 
of a branch. In the axil of ZY’ the rudimentary scale leaf, vs/, 
appears on the left of the growing point gf”). At the base of 
L1V we find the scale leaf (vs/) in its normal position, and also 
on the left of the growing point point the first vegetative leaf of 
the branch, 4U"). The axils of L777 and L¥ show successively 
advanced stages until in Z/ appear four leaves of the branch besides 
the scale leaf;—4, 41), 2,() and 4,(). Moreover in the axils 
of 4) and 4 appear young growing points to form branches of 
a second order. 
Such a growing point under ordinary conditions will develop in 
a regular way for some time, the leaves and axillary shoots appear- 
ing in acropetal succession and the nodes of increasing length. 
basipetally, according to their age. This stage is represented in 
Pl. I, fig. 2, a sketch from a living specimen. 
Sooner or later, however, in the course of the development of 
the system, its regularity becomes more and more modified to suit 
environmental relations, a condition which is of course true of any 
branch system. PI. II, fig. 6 is a drawing from nature of the upper 
portion of a plant whose vegetative branch system has undergone 

