406 BOTANICAL GAZETTE [DECEMBER 
thallia with certainty. Certain prothallia previously figured (4) 
seem to suggest them, but at that time prothallia of L. obscurum 
were unknown, and identification was made upon comparison with 
figures published by other writers. It is entirely possible that 
those specimens may have been misnamed. There is also the 
possibility that antheridia may occasionally take the form men- 
tioned in species other than the one under discussion. Figs. 
79-81 show the habit of growth of these organs. The prothallia 
are all shown under a magnification of ten, so that a glance at the 
figures will give the relative size of the individuals figured. Fig. 
81 shows a mass enlarged. 
A cross-section of the prothallium through two antheridial 
ridges is shown in fig. 74. It is apparent that the masses arise from 
the tissue lying within the outer border ring. For sake of clearness, 
one region is represented as without the endophytic fungus. As a 
matter of fact the fungus. does invade the antheridia through the 
opening shown by the opercular cells in figs. 82 and 89. It has not 
been located for certain in the cells of the antheridia walls, but it 
is possible that the fungus is present in the intercellular spaces. 
Because of the intimate relationship between the sperms, and 
possibly the wall cells, with the fungus, it seems very likely that 
the unusual growth of antheridial masses may be explained by 
symbiosis. There is no indication of a pathological condition of 
the sperms. The writer has never seen the fungus in the antheridia 
of any other species of prothallia of Lycopodium. It is well known 
that an endophytic fungus present in the prothallia of certain ferns 
will cause abnormal growth of tissue. 
The individual antheridia arise acropetally from the groove. 
There is no primordium for the mass. This is a secondary growth, 
although it arises very early. Figs. 87 and 88 show the antheridium 
initial and the first division. The mature detail is shown in figs. 
82 and 89. In this species four opercular cells may often be 
observed. I have never seen it for certain in any other species. 
The figures representing these cells were made by camera lucida. 
In all of the prothallia sectioned, numerous retarded antheridia 
were*observed. They were distributed throughout the older regions 
of the plant, and had the ordinary appearance of the male organs, 
