Lycopodiales. 193 
contemporary representatives of other phyla before acquiring a 
definite strobilus. 
The gametophyte of Lycopodium has been the subject of 
careful comparative study by Dr. Lang (15). In the Lycopodium 
cernuum type of prothallus, which is characteristic in all essentials 
of L. inundatum and L. salakense, and of Phylloglossum, there is a 
primary tubercle bearing one or two more or less filamentous out¬ 
growths, that later become thickened so as to be externally 
indistinguishable from the tubercle. The latter is almost always 
occupied by an endophytic fungus, and the upper part of the 
prothallus contains chlorophyll. In L. cernuum and L. inundatum 
the prothallus is crowned by leaf-like lobes absent from L. salakense 
(15) and Phylloglossum (22). Dr. Lang points out that the 
prothallus of L. selago often shows a distinct resemblance to this 
type. Normally it is subterranean and a more or less cylindrical 
body devoid of chlorophyll, but when exposed artificially or naturally 
to light it develops a considerable amount of chlorophyll (15). This 
at once suggests a comparatively recent origin for the subterranean 
prothallia from a form such as that found in L. cernuum. This 
prothallus appears to be more or less independent, though the 
endophytic fungus associated with it may indicate a partially 
symbiotic habit. No primary tubercle is found in L. selago, but 
the germination of its prothallus has not been observed and in later 
stages the primary tubercle is often unrecognizable. The leafy 
lobes are not of course found in this subterranean form, but these 
are absent in L. salakense which is distinctly of the L. cernuum- type. 
Dr. Lang writes: “ Besides this form of prothallus, the resemblance 
of which to the L. cernuum- type will be evident, elongated cylindrical 
forms which originate by growth becoming localized in one portion 
of the meristematic zone are found. The interest of these will be 
seen in connection with the L. Phlegmaria-type of prothallus” (15). 
Dr. Lang’s conclusion that the L. selago- type of prothallus, found 
also in L. complanatum and L. alpinum, originated from the 
L. cernuum-type by adaptation to a subterranean habit seems 
justified. The prothalli of L. annotinum and L. clavatum are not 
unlike the prothallus of L. selago, but the meristem gives rise to an 
expanded, more or less irregularly lobed, portion, much larger than 
the conical body to which it is attached. These species develop 
chlorophyll. The other species of Lycopodium in which the 
gametophyte is known are all of them tropical and the prothallus is 
a highly branched structure. This form of prothallus is known as 
