Vascular Anatomy of Platycerium. 313 
is composed of four strands, which increase hy division in the 
petiole. In the younger leaf, the temporary commissure begins to 
appear, but never becomes complete (Fig. 2, 78). 
Fig. 2.— Platycerium alcicorne (1-19) and P. cethiopicum (20-21). 1-19 a scries 
of transverse sections of a young plant of P. alcicorne , arranged from below 
upwards, showing formation of leaf-trace (19), formation of vegetative bud 
(6-10), and petiole of leaf (10-19); a, Vascular strands of vegetative bud. 20, 
21, Transverse sections of base of petiole of P. csthiopicum. 
In an older plant of P. alcicorne (Fig. 3), it is more readily 
seen that the vascular system is a “ perforated ” dictyostele, con¬ 
sisting of a ring of meristeles, which are much subdivided, and form 
an anastomosing network. On the dorsal surface of the rhizome, 
the leaves come off right and left, while the whole ventral surface 
has a thick covering of rootlets, which are given off from the 
ventral meristeles and traverse the cortex obliquely. A thick ring 
of sclerenchyma surrounds the vascular system, and the rootlets 
break through this and are distinguished in the cortex by a dark 
band surrounding them. The ring of sclerenchyma does not 
border directly on the epidermis, but is separated from it by some 
layers of thin-walled parenchyma. The meristeles themselves are 
simple in structure, consisting of xylem intermixed with paren¬ 
chymatous cells, surrounded by phloem and pericycle. Outside the 
endodermis is a sheath of sclerenchyma. 
In the series of sections which I have figured, and shall 
describe, the plant of P. alcicorne was almost full grown. The 
sections were cut through the bases of three foliage-leaves. The 
