of P ihil aria globulifera , L. 251 
the subsequent divisions are to be looked upon as segments 
of these primary organs. Leitgeb and Arcangeli assert on 
the other hand that there is a regular formation of octants. 
My own observations do not confirm either view, but in- 
dicate that the quadrant-wall was the one which separated 
the primary organs, and that the quadrants are of equal 
morphological importance. In regard to the formation of 
octant-walls, while they are formed in the anterior quadrants, 
the corresponding walls in the root- and foot-quadrants form 
very unequal angles with the basal wall, so that the resulting 
cells are of unequal size. From this fact (see PL XIV, 
Figs. 5, 6), it is possible to distinguish the primary organs of 
the embryo as soon as these walls are formed. 
In order to avoid confusion it will be best perhaps to take 
up each quadrant separately and follow its development in 
detail. 
The Leaf. 
The leaf-quadrant, as already stated, undergoes division by 
an octant- wall into two entirely similar cells. Each octant 
now divides by a curved wall (PI. XIV, Figs. 4-5), meeting 
basal and octant walls so as to form two cells, one retaining 
much the same form as the octant, that is tetrahedral, and 
appearing in section triangular ; the other quadrilateral, as 
seen in section. The two tetrahedral cells function for a short 
time as apical cells, forming three series of segments corre- 
sponding to their lateral faces. Each segment next divides into 
an outer and an inner cell, from the former of which is derived 
the epidermis, from the other the ground -tissue and the 
vascular bundle. Sooner or later this apical growth ceases, 
and the growth is confined to the basal part of the leaf. The 
cessation of apical growth occurs about the fourth day, and 
before this the leaf begins to elongate (PL XIV, Fig. 16 a). 
Not infrequently one of the cells persists longer than the 
others, and can be detected after the leaf has assumed its 
conical form and become noticeably larger than the other 
members of the embryo (PL XIV, Fig. 15). In such cases the 
