of Lycopodhtm clavatum , L. 313 
three which present the L.cernuum type, are terrestrial plants 
not specially attached to soil containing humus. The plants 
of the L. Selago, complanatum , and clavatum types of pro- 
thallus live for the most part on moors or in open woods, 
places where the soil is rich in humus. The rarity of young 
plants, unless in exceptional circumstances due to human 
interference, is an index of the difficulty encountered before 
the spore can succeed in developing into a prothallus, a dis- 
advantage only compensated by the capacity for vegetative 
reproduction of the sporophyte by a creeping habit or by 
means of bulbils. Lastly, all the species which possess the 
L. Phlegmaria type of prothallus are epiphytes. 
It would be strange if the genetic affinities of the species 
of Lycopodium were found to coincide exactly with these 
biological divisions. More probably when all the facts are 
known such a parallelism will be found to be disturbed by 
instances of independent adaptation to similar conditions. 
Only the investigation of the remaining species can confirm 
or disprove the correctness of this mode of regarding the 
differences of the gametophyte and young plant ; it appears 
to the author to be indicated on the imperfect data we at 
present possess. Until further facts are available its general 
discussion as one possible interpretation of the facts will be 
sufficient. It follows from such a view that, while a complete 
critical study of the gametophyte may afford valuable assis- 
tance in determining affinities within the genus Lycopodium, 
the characters of the prothallus cannot be safely taken by 
themselves, since the variations in them have been shown to 
stand in 'such close relation to the conditions of life, and 
especially to the saprophytism of certain species. The 
characters of the less modified sporophyte must be used to 
check those derived from the gametophyte and should have 
greater weight. On these grounds it seems inadvisable to 
subdivide the genus Lycopodium as suggested by Bruchmann. 
It may be hoped that the discovery of the prothallus in 
Phylloglossum , Psilotum , and Tmesipteris will cast further 
light on the relationship of the existing Homosporous Lyco- 
