526 Boodle —Comparative A natomy of the 
SCHIZAEA DICHOTOMA, SMALL FORM. 
Two plants, collected by Mr. R. H. Yapp and determined 
by him as a small form of S', dichotoma , will now be described. 
One of these plants bore two fertile leaves, but from the 
structure of the stem it is probable that both specimens were 
young plants 1 ; the primary root, however, was not present in 
either. Fig. 26, F, illustrates a protostelic stage near the base 
of one of the specimens. Higher up one finds the transition 
to the mature type of structure. It takes place in much the 
same manner as in seedlings of S . pusilla , but the dimensions 
are greater than in the latter species. Only a few details 
need be given. In both specimens two or three parenchyma- 
tous cells appear in the xylem and soon increase to form 
a fair-sized pith, which shows no trace of internal phloem. 
In one specimen a very small endodermal pocket was formed 
in connexion with an early leaf-trace (i. e. not far above the 
protostelic region), while at a roughly corresponding level 
in the other specimen a small isolated tube of endodermis 
appeared in the central parenchyma. One slightly later node 
in each specimen was remarkable for the small difference 
in size between leaf-trace and stele, and the resemblance in 
shape of their respective xylem-masses, the shape being 
flattish-crescentic 2 . 
Deductions from the Ontogeny. 
If the transitional region of the stem of S. pusilla be com- 
pared with that of Anemia Fkyllitidis, it is seen that, in these 
two plants 3 , the behaviour of the xylem and the mode of 
occurrence of soft-walled elements within it are very similar, 
but the nature of the soft-walled elements is different. In 
Anemia they comprise sieve-tubes at an early stage, while in 
Schizaea pusilla this is not the case. Nor does phloem occur 
1 They may be simply young plants of the typical S. dichotoma . 
3 One of these nodes when first examined was taken for a dichotomy. 
3 Examination of the structure of older seedlings of S. pusilla than that 
described in the present paper, and of known seedlings of S. dichotoma , is of course 
highly desirable. 
