Fteridophytes. Are they vestigial? 249 
such primitive characters of the sporophyte? Taking into 
account the characters of its mature sporophyte both external 
and internal, I think we must regard L. Selago as primitive, 
and that it is so in the embryo as well as in the more mature 
sporophyte : its embryo quickly forms assimilating leaves, and 
its early nourishment is thus simply provided for, without 
the formation of any protocorm or protophylls. 
The following considerations may help towards some alter- 
native view of the protocorm and protophylls more in accord- 
ance with the fact of their absence in L. Selago , which on the 
above grounds we regard as a primitive species. The embryo 
Lycopod seems prone to parenchymatous swelling ; two such 
swellings, somewhat similar in structure, but differing in 
place of origin and in function, are known, viz. the enlarged 
‘foot’ of L. clavatum and annotinum, which originates from 
the lower tier of the embryo, and is intra-prothallial ; and the 
protocorm of the cernuum type, which originates from the 
upper tier of the embryo, and is extra-prothallial. The former 
acts as an haustorium, the latter as a place of storage. A genus 
which shows two types of parenchymatous swelling in two 
distinct types of embryo, while both are absent from other 
species, cannot be expected to have ever had one of those 
as a constant feature in its ancestry. This consideration 
makes me doubt any general application of the theory of the 
protocorm in the genus Lycopodium. I should look upon 
these parenchymatous swellings, whether of the enlarged 
intra-prothallial foot or of the protocorm, as opportunist 
growths rather than as persistent relics constant in the 
ancestry. Phylloglossum , with its large protocorm, would 
then be the extreme type of a line of embryological special- 
ization, not a form preserving the primitive embryological 
characters of the whole race 1 . 
1 This discussion leads me back to a similar one written in 1882, in a paper 
on Gnetum Gnemon (Q. J. Micr. Sci., xxii, p. 277), in which the conclusion was 
arrived at that the foot in vascular plants at large is not to be regarded as a clearly 
defined morphological member ; it may rather be looked upon as a swelling of 
tissue, which arises only when and where required for the nutrition of the embryo. 
Doubtless in certain circles of affinity there is a degree of constancy in position and 
