//. The Ovule of Stangeria paradoxa, 283 
vertical rows, which are not, however, strictly continuous with 
the rows of cells composing the nucellus. The latter is 
marked off from the integument by a series of flattened cells, 
which can be traced down from the place of separation of the 
free portions of integument and nucellus. Within this limit 
the nucellus is composed of vertical rows of cells, from five 
to seven of which are present in a median section. These 
rows can be traced to just below the epidermis, which is 
a definite layer of cells undergoing anticlinal divisions only. 
Although the continuity of the vertical cell-rows is usually 
clearly recognizable, a distinction is already apparent in the 
character of their component cells between the tip of the 
nucellus and an oval group of larger cells, which in older 
ovules becomes more sharply defined as the sporogenous tissue. 
About the centre of this sporogenous group a cell of larger 
size than the rest can be distinguished (Fig. 2). The nucleus 
of this cell, which is the mother-cell of the embryo-sac, is 
somewhat larger than those of its sister-cells. At this stage, 
however, the embryo-sac mother-cell has not become vacuo¬ 
lated. The position of the vascular bundles supplying the 
ovule is indicated at the base of the latter by desmogen- 
strands. As the ovule increases in size its different parts 
become more clearly defined from one another, and the pro¬ 
jecting portions of the integument and nucellus-apex more 
prominent. The increase of the latter structure is due to 
periclinal divisions in the tissue just beneath the epidermis. 
The mother-cell of the embryo-sac, situated in the centre 
of the now clearly limited sporogenous tissue, has increased 
considerably in size and become vacuolated; it is still undivided, 
the large nucleus being situated towards the micropylar end 
of the cell, the wall of which has become thicker than the 
walls of the neighbouring cells. Fig. 3 represents the nucellus 
of an ovule at this stage. 
The mother-cell of the embryo-sac in Stangeria undergoes 
considerable increase in size before dividing. The order of 
the divisions could not be accurately followed, but, as Fig. 4 
shows, the mother-cell first divides into a larger lower and 
