204 BOTANICAL GAZETTE [ocrouEn 
between the expospore and endospore shows signs of dissolution; ¢, spore mem- 
brane (includes everything between a and g); @, portion of spore membrane 
becoming transformed into exospore; §, endospore. 600. 
Fic. 8. Small portion of median section of apical region of megaspore more 
advanced; the protoplast 6 with the endospore g on its outer face has expanded 
until it has come to lie close to the outside e; the undifferentiated part h of the 
spore membrane has almost entirely disappeared; e¢, exospore; g, endospore 
(black line); /, layer of granular matter which is all that remains of region 
between ¢ and g in fig. 7. X60. 
Fic. 9. Apical region of median section of older megaspore; the mother cell 
membrane has disappeared entirely; b, protoplast increasing rapidly; e, exospore; 
g, endospore (increasing in thickness by successive laminae formed on its inner 
surface in the vicinity of the nucleus). 600. 
Fic. 10. Portion of apical region of median section of mature megaspore in 
the region of the nucleus; the protoplast has increased in thickness at the expense 
of the central vacuole near which the nucleus lies; the protoplasm contains much 
proteid matter which stains deeply; e, exospore; g, endospore. X 600. 
Fic. 11. Part of median section of female gametophyte after cell walls have 
begun to form; the proteid granules have increased in number and in size; & 
exospore; g, endospore; mm, nuclei. 600. 
PLATE XI. Selaginella Emmeliana. 
Fic. 12. Megaspore mother cell in optical median section, after the formation 
of the spore membrane. 1250. ‘ 
Fic. 13. Median section of megaspore mother cell in process of division into 
tetrad; nuclear plates forming; «x, nuclear plate; 4, spindle fibers. X 1250. 
Fic. 14. Median section of megaspore tetrad showing com Jetion of spore 
membrane along the nuclear plates. 1250. 
Fic. 15. Median section of somewhat older tetrad, 
ness of spore membrane between the protoplasts of the spores; 
ion of a layer of 
th the convoluted 
showing increase in thick- 
protoplasm 
border becomes the exospore, the inner region in contact with the ig 
becomes the endospore; outside of the forming exospore, at 
mother cell membrane, is a layer of the undifferentiated spore membran?s y 
portion of spore membrane in process of transformation into coats; ¢ regio” 
exospore; /, region of endospore; m, undifferentiated portion of spore membrane: 
1250. ae 
Fic. 17. Nearly median section of tetrad showing farther differentiation 
exospore and endospore; two megaspores show the effect of the m api 
strain between exospore and endospore which has a tendency to split the &* a 
into two layers; stages between fig. 16 and fig. 17 were not foun among $f oh 2 
hundred preparations; the transformation of the spore membrane into eats © S 
