Gametophyte of Selaginella. 427 
groups of sperm-cells by a process of free cell-formation, like 
that of ascospores, is, to say the least, improbable, and must 
be positively demonstrated before it can be accepted. 
The Older Gametophyte. 
The later stages of the gametophyte, the structure, and 
development of the archegonium were not further investigated, 
as these have been sufficiently described and figured by the 
writer before. 
Summary. 
1. Fitting’s account of the development of the spore- 
membranes and the character of the protoplast in the young 
spore was confirmed. 
3. Except for the mistake of interpreting the young 
protoplast as the nucleus of the young spore, the account 
previously published by the writer was found correct in every 
particular. 
3. The nuclei in Selaginella Kraussiana are uniformly 
distributed through the cytoplasm of the young spore ; later 
they are more numerous in the apical region, where the cyto- 
plasmic layer is also thicker. 
4. No preliminary blocking out of nucleated areas takes 
place, but cell-walls are formed at once. The primary cells 
(‘ areoles ’) are at first open below. 
5. A definite cellular body (primary prothallium) is formed 
at the apex of the spore. This is a disc, usually composed of 
three layers of cells in its central part. The inner walls of the 
lower layer of cells become thickened, and form a diaphragm 
separating the primary prothallium from the undivided spore- 
cavity below. 
6. The cytoplasm of the spore-cavity increases rapidly in 
amount, so that the central vacuole becomes much reduced 
in size, but it is still evident when the spores are shed. Ulti- 
mately it becomes completely obliterated. Except in the 
very latest stages it is quite free from granular contents, 
appearing entirely empty in microtome sections. 
