304 Lang . — The Prothallus 
the L. Phlegmaria type of prothallus. As in L. cernuum , the 
sexual organs of L. Selago are confined to the terminal region, 
the youngest being found nearest to the merismatic zone. 
Associated with them, however, are found numerous hairs 
(the paraphyses) consisting of a single row of cells ; these 
structures, which are known in all the saprophytic Lycopodium 
prothalli, are not found in those of the L. cernuum type. The 
sexual organs themselves do not appear to differ fundamentally 
from those of that type, the antheridia being closely similar, 
while the archegonium has a slightly longer neck, the canal 
being occupied by a central series consisting of the ovum and 
not more than six canal-cells. 
Thus as regards external form and sexual organs, the 
prothallus ofZ. Selago might reasonably be regarded as having 
originated by modifications in relation to its wholly sapro- 
phytic mode of life from a type of gametophyte resembling 
that possessed at the present day by L. cernuum, &c. The 
prothalli of the other European species, which are all sub- 
terranean saprophytes, present greater differences in these 
respects, which can be mentioned more briefly. Those of 
L. clavatum and annotinum are, in a young stage, not unlike 
that of L. Selago. As the activity of the merismatic zone 
between the vegetative and generative halves proceeds, 
however, the upper portion of the prothallus becomes greatly 
extended horizontally, the conical portion of the young 
prothallus appearing as an insignificant projection from this 
flattened part which later becomes more or less irregularly 
folded. The description in the earlier part of this paper will 
show the similarity of arrangement of the sexual organs in 
this species to that in L. Selago. It must be added to this, 
however, that paraphyses develop when the prothalli are 
grown at the surface of the soil ; under such circumstances 
chlorophyll is also formed. It has also been seen that the 
increased length of the archegonium-neck in this species is 
mainly due to a growth of surrounding cells ; the central 
series consists of ovum and seven canal-cells. 
The prothallus of L . complanatum (with which that of 
