Bowenia spectabilis , Hook . f. 481 
tissue composed of small cells. The commencement of 
branching is indicated by a broadening of the apex, which 
is succeeded by the longitudinal division of the apical 
meristem into two apparently equal portions. But the 
dichotomy is only apparent, for one branch soon shows 
itself to be stronger than the other. None of the branches 
grow much in length before undergoing further branching 
of the same character, and to this is due the characteristic 
‘coralloid’ appearance of the head of the root (Fig. 2). 
The apogeotropic root arises, like the ordinary lateral root, 
endogenously opposite a protoxylem-group of the main root. 
A cylinder of cambium, continuous with the cambium of the 
main root, appears in the tissue of the young root before 
it has yet reached the surface, and gives rise to secondary 
xylem- and phloem-elements which are continuous with the 
corresponding elements of the main stele (Fig. 8, a. ph . 2 , 
a. xy 2 ). The primary structure of the stalk is similar to 
that of the ordinary lateral root. The stele is diarch, or 
more frequently triarch (Fig. 9). Primary growth in thickness 
is very much less than in the ordinary root : pith is usually 
absent, or, if present, very small in amount. A cambium 
appears on the inner face of each phloem-mass, but never— 
as far as was observed — forms a complete ring round the 
primary xylem-groups (Fig. 9, cb.). A single phellogen-layer 
arises in the external cortical tissue, an inner layer not being 
developed in the pericycle as in the ordinary root. Starch 
is found in the cells of the ground-tissue : many of the cells 
are filled with cluster-crystals of calcium oxalate, which are 
especially abundant in the cells of the pericycle and inner cortex. 
The peripheral (‘ piliferous ’) layer of the coralloid head 
is composed of cells which are radially elongated, their outer 
ends being free from one another (Fig. 10, p.). This layer 
gives a villous appearance to the surface which is obvious 
to the naked eye. A phellogen-layer forms in the external 
cortex, beneath the papillose layer (Fig. 10, pi.), continuous 
with the phellogen-layer in the stalk. Eventually the 
papillose layer is cast off and the whole root is enveloped 
