and Helminthostachys zeylanica. 27 
initial cell. In longitudinal section this is seen to be triangular 
in form (Fig. 10) ; in transverse section it is four-sided 
(Fig. 11). The apical cell is thus a four-sided pyramid with 
a convex base, and segments are cut off in regular succession 
by walls parallel to the four sides. Each segment becomes 
subdivided by periclinal and anticlinal walls, the general 
direction of which will be evident from the figures. These 
first periclinal divisions do not appear to mark off definite 
structural regions, but a short distance behind the apex a 
superficial zone, in which the divisions are mostly parallel to 
the surface, can be distinguished from the central tissue of the 
branch. It is in this outer zone that the sexual organs 
originate, periclinal divisions in the cells between them keeping 
pace with their growth. Slightly further from the apex the 
tissues have become fully developed, but are still free from 
the endophytic Fungus. In this region the sexual organs 
become mature and open. On passing to the still older part 
of the branch, the Fungus is found occupying the internal 
tissue. These regions are shown in the longitudinal section 
through a branch (Fig. 12), which also shows the slight histo- 
logical differentiation in the prothallus, due to the central 
cells being somewhat elongated. In transverse section (Fig. 
13) these central cells are rounded, while towards the periphery 
of the section the cells are flattened parallel to the surface. 
The section represented in this figure passes through the 
region in which the endophyte is just making its appearance. 
The short wide hairs (Fig. 14), the appearance of which 
in surface view has been seen, originate from single super- 
ficial cells of the branch a short distance behind the apex of 
the latter. Each cell giving rise to a hair projects as a conical 
papilla ; the projecting part is then cut off by a periclinal 
wall. The hair remains unicellular h Its nucleus, which is 
often suspended in the centre of the cell, may be round or be 
more or less elongated in the direction of the length of the 
1 The abundance of these hairs in this epiphytic prothallus suggests a com- 
parison with the multicellular paraphyses known in the prothalli of several 
species of Lycopodium and especially well developed in some epiphytic forms. 
