xiii LYCOPODINEM 513 



figures, are astonishingly cell-like in appearance. Until it can 

 be conclusively shown that these are not really cells, the state- 

 ment must be accepted with a certain amount of reservation. 



A Vecent examination by the writer of some of the germi- 

 nating stages of the microspore of S. Kraussiana has shown 

 beyond question that in this species' at least, BelajefFs statement 

 as to the formation of a peripheral layer of cells about the sperm 

 cells is correct. There was no trace of any vacuoles, the granu- 

 lar cytoplasm filling the spore completely and the walls sepa- 

 rating the peripheral cytoplasm from the central area were clear 

 and unmistakable. No attempt was made to verify the exact 

 succession of the division walls. 



The Macrosporc and Female Prothallium 



The formation of the female prothallium begins while the 

 spore is still within the sporangium, and long before it has 

 reached its full size. 



At an early period, shown first by Fitting ( i ) , but later 

 verified by Miss Lyon (2) and Campbell (25), the protoplast 

 of the young macrospore separates from the inner spore mem- 

 brane (Fig. 296, A), and the outer spore-membrane increases 

 rapidly in size, so that a wide space separates the protoplasmic 

 vesicle from the inner spore-membrane. The minute globular 

 protoplast was mistaken by all the earlier observers for the pri- 

 mary nucleus of the macrospore, as it is very evident through 

 the transparent membrane at this time. The real nucleus is 

 very small and divides very soon, but the cytoplasmic layer re- 

 mains extremely thin. As the spore develops, the cytoplasmic 

 vesicle rapidly increases in diameter and finally comes again into 

 close contact with the endospore, or inner cellulose membrane 

 (Fig. 296, B). There is a middle lamella or mesospore (m), 

 which is very conspicuous in the early stages, as it is also, ex- 

 cept at the apex of the spore, quite free from the thick outer coat, 

 the exospore. The space between the mesospore and exospore 

 is filled with a substance which stains faintly, and undoubtedly 

 contains material which is used by the growing membranes. 



The nuclei (n) are small, and while the cytoplasmic layer 

 remains thin, are flattened. Later they increase rapidly in num- 

 ber, and with the thickening of the cytoplasmic layer, become 

 globular in form. At first they are pretty uniformly distrib- 

 uted, but later are more numerous at the apex of the spore; but 

 33 



