CHAPTER XXVI. 
EMBRYOLOGY OF THE LYCOPODIALES. 
(A) ELIGULATE LYCOPODIALES. 
In Chapter XIV. the modern aspect of comparative embryology of the 
sporophyte has been discussed. For reasons there stated it was concluded 
that only a minor place in comparisons is to be conceded to the details 
of the initial embryology of the sporophyte: the characteristic form of 
the mature plant, established after the earlier and in considerable degree 
adaptive phase of development is past, is held to give a more reliable 
basis for argument than does the embryonic state. Especially is this the 
case among the Pteridophyta, and it happens that the Lycopods supply 
examples of peculiar interest in relation to such questions; they will serve 
at once as an illustration, and as a test of the principle thus briefly 
stated. For in the general conformation of their mature sporophyte there 
is a remarkable uniformity throughout the whole phylum: the differences 
are those of secondary*detail: the main facts of plan and proportion of 
their shoot- and root-systems, of their branching, and of the relation of 
the sporangia to the other parts, leave no doubt of a natural affinity as 
based on the character of the mature sporophyte. But in the embryology 
there are points of marked divergence, which may be more or less clearly 
correlated with differences of character of the parent prothallus. There is 
reason to think that within the genus Lycopodium the prothallus and embryo 
have undergone a cognate divergent development from a central type, 
though the mature sporophyte has still retained a substantial uniformity. 
The differences in character of the prothallus within the genus Lycopodium 
are found to be those of habit and of mode of nutrition rather than of 
fundamental structure. According to their mode of life three main types 
may be distinguished, which, however, graduate into one another in such 
a way as to suggest their intimate connection by descent from some 
common source. The type shown by JZ. cernuum, and shared also by 
L. inundatum and salakense, consists of a massive cylindrical thallus, of 
which the conical lower part is sunk in the soil, while the upper part is 
