300 Lang . — The Prothallus 
knowledge of the life-history is extended to other species, but 
it appears advisable to state it. In order to do so it will be 
necessary to briefly discuss the characteristics of the Lyco- 
podium prothalli now known. It would be tedious to compare 
them point by point in every case, but it may be stated that 
in drawing conclusions the germination of the spore, form 
and structure of prothallus, position of meristem, position and 
structure of the sexual organs, and the embryogeny have 
been taken into account. Further, the results have been put 
into relation with the habit of the prothallus and that of the 
sporophyte. Those prothalli which belong to the type of 
L. cernuum will in the first place be considered, and those 
of the other species afterwards compared with this type. 
The prothallus of L. cernuum , with which those of L. inun- 
datum and L. salakense agree in all important respects, is 
a small body of cylindrical form which grows upright on the 
surface of the soil. On the germination of the spore an oval 
or spherical mass of tissue (the primary tubercle) is formed, 
from the surface of which one or more short filaments 
originate. By the further development of one of these the 
cylindrical portion of the prothallus is formed. Sometimes 
the primary tubercle can be recognized at the base of the 
cylindrical portion of a prothallus which has attained its full 
size. In other specimens these two regions are not to be 
distinguished on external examination. The latter state of 
affairs is the usual one in L . inundatum , while in the other 
two species the tubercle is as a rule recognizable. The meris- 
matic region of the young prothallus is not at first localized. 
Ultimately, however, a zone of merismatic tissue can be dis- 
tinguished extending completely round the upper part of the 
cylindrical portion of the prothallus, but not terminal. As 
the cells of the zone become converted into permanent tissue, 
they contribute on the lower side to the growth of the cylin- 
drical portion ; while above the meristem green expanded 
lobes are formed, at the bases of which the sexual organs are 
situated. These lobes may be well-developed structures, as 
in L. cernuum and L . inundatum , but in Z. salakense they are 
