DIV. I 



MORPHOLOGY 



85 



are examined with a magnifying glass (Fig. 98). It then appears flat 

 (Fig. 99) or convex (Fig. 98 t ? ), and sometimes distinctly conical 

 (Figs. 100, 102). The rudiments of the leaves (/) and of lateral 

 branches (g) arise laterally beneath the tip and appear as closely- 

 crowded exogenous projections or bulges of the surface. The leaves 

 arise in acropetal order and become larger on passing farther from 

 the apex, as is clearly shown in transverse sections of the growing 

 point (Fig. 99). 



The growing point and the young leaves, which only arise from 

 the embryonic part of the apex, both consist of meristematic tissue. 

 In the majority of the Ferns and in the Horsetails a single apical cell 



J 



FIG. 98. Apex of a shoot of a phanerogamic plant. 

 v, Vegetative cone ; /, leaf-rudiment ; g, rudi- 

 ment of an axillary bud. (x 40. After 

 STRASBCRGER.) 



FIG. 99. Apical view of the 

 vegetative cone of a shoot 

 of Euonymus japonica. 

 (x 12. After STRAS- 



BTTRGER.) 



is found at the summit of the growing point (Fig. 100 t). It has the 

 form of a three-sided pyramid (tetrahedron) with a convex base. 



The apical cell (Fig. 100 t, 101 A) of the main shoot of the Common Horsetail 

 (Equisetum arvense) will serve as an example. Viewed from above (Fig. 101 A] it 

 appears as an equilateral triangle in which new walls are successively formed 

 parallel to the original walls. Each segment (', S") becomes further divided by 

 partition walls. In the Pteridophyta which have apical cells the leaf rudiments 

 (/> /', /") usually commence their development with an apical cell which cuts off 

 the rows of segments (/). The activity of this usually ceases, and the development 

 of the leaf is continued by marginal growth due to a number of equivalent two- 

 sided cells. This is the case, for example, in Equisetum. The lateral buds (g} also 

 start from a single cell that becomes the apical cell. 



In the Lycopodiaceae, among the Pteridophyta, and in Phanero- 

 gams, there is no such single apical cell at the growing point. In 



