304 Lang.—Development of Cycadean Sporangia . 
forward, while indications are not wanting that the compara¬ 
tive study of these genera will afford it further support. As, 
however, the material collected does not as yet allow of 
a sufficiently wide comparison, this will be deferred for the 
present. Until this is done, however, the view that the 
Cycadean ovule is the equivalent of the male sorus can only 
be put forward as a provisional statement, which will have 
to be carefully tested by a comparative examination of the 
whole series of living Cycads, in the light of the evidence 
obtainable from extinct forms. 
EXPLANATION OF FIGURES IN PLATES 
XVII AND XVIII. 
Illustrating Dr. Lang’s paper on the ovule of Stangeria pai'adoxa. 
PLATE XVII. 
Fig. 1. Young sporophyll, bearing two ovules, viewed from its point of attach¬ 
ment to the axis; the ovules are situated within the margin on the abaxial surface. 
= cut surface of stalk of sporophyll. ( x 25.) 
Fig. 2. Median longitudinal section of a young ovule; the free portions of 
nucellus and integument are just recognizable, and the mother-cell of the embryo- 
sac can be distinguished in the centre of the sporogenous tissue. ( x no.) 
Fig. 3. Similar section of a slightly older ovule, the integument being omitted; 
the mother-cell of the embryo-sac has increased in size and become thicker-walled 
but is still undivided; the sporogenous tissue is shaded. ( x 375.) 
Fig. 4. Mother-cell of embryo-sac divided into two segments, with the adjoining 
sporogenous tissue; in the cells of the latter the spherical bodies described in the 
text are visible. ( x 375.) 
Fig. 5. Mother-cell of embryo-sac divided into three segments, the lowest of 
which is destined to become the embryo-sac. (x 375.) 
Fig. 6. Young embryo-sac, still uni-nucleate, with the two sister-cells in a crushed 
condition at its upper end. ( x 375.) 
