1905] LYON—THE SPORE COATS OF SELAGINELLA 295 
very rapid; e, exospore; /, endospore; m, undifferentiated part of spore mem- 
brane; ~, outer sculptured part of exospore (so-called perinium); g, strained 
region in exospore. X 375 
Fic. 18. Nearly median section of a megaspore at a later stage than fig. 6; 
the specimen was slightly shrunken, which gives the appearance of a cleft in the 
exospore traversed by some unbroken strands; the undifferentiated portion of 
the spore membrane between the exospore and the protoplast (jig. 16, m) has 
been transformed into endospore; at this stage the protoplast increases in diame- 
ter rapidly; e, exospore; jf, endospore; g, stretched and partially split region in 
the substance of the exospore. 375. 
Fic. 19. Small portion of the median section of a nearly mature megaspore 
in the apical region; coats fully formed; the cleft separating the exospore into 
two layers is probably due to the action of reagents; e, exospore; f, endospore; 
§, cleft in substance of exospore; m, undifferentiated remnant of spore membrane. 
X375: 
