294 Lang.—Development of Cycadean Sporangia. 
coherent tissue, are the embryos (Fig. 30). The embryo is 
usually wedge-shaped, but exhibits no greater differentiation 
of its tissues than in the earlier stage. One of the embryos 
has, as Fig. 30 shows, by this time become larger than the 
others, and penetrates more deeply into the prothallus. This 
isolation of the successful embryo is more apparent in Fig. 31, 
which represents the largest embryo found in an unsown seed. 
In the process of elongation of the suspensor its base is often 
forced upwards towards the neck of the archegonium, the 
contents of which have, as a rule, by this time entirely dis¬ 
appeared. 
The embryo in one seed, which had been placed under 
suitable conditions for germination in the Edinburgh Gardens, 
was examined after some weeks. As Fig. 32 shows, it was 
not firmly embedded in the prothallus, but hung free on the 
suspensor into the cavity formed by the destruction of the 
surrounding tissue. The embryo had increased somewhat in 
size, but showed no advance in morphological differentiation, 
no indication of the cotyledons being apparent: the tissue 
composing it resembles an apical meristem more closely than 
it did at earlier stages. 
In the next stage obtained the primary root of the seedling 
was already over an inch in length. The seedling resembled 
those of other Cycads at this stage. The anatomy agreed 
generally with the description by Worsdell*, founded on 
a somewhat more advanced seedling of Stangeria. It would 
appear to be a justifiable inference from a comparison of the 
embryos figured in Figs. 31 and 32 with the seedling, that 
the intimate connexion, which ultimately obtains between 
cotyledons and prothallus, is effected by the origin of the 
former on an embryo hanging free in the absorption cavity. 
This explains the way in which the stem-apex is freed from 
contact with the prothallus, and is in a position to be carried 
outside the seed by intercalary growth of the cotyledons when 
germination takes place. 
One or two deviations from the normal embryogeny may 
1 Journ. Linn. Soc., vol. xxxiii, p. 447, 1898. 
