i 9 i S ] HUTCHINSON— MALE GAMETOPHYTE OF PICEA 291 



the microspore just prior to germination" (15). When two evan- 

 escent cells are cut off, these divisions take place before the increase 

 in size. They follow one another in rapid succession; all stages 

 of the first two primary divisions are to be found in the same spo- 

 rangium. A resting period, that is, a period during which mitosis 

 ceases, but during which there is a great increase in size and ap- 

 parently in food supply, precedes the formation of the functioning 

 antheridial cell, whether it be the first, second, or third primary 

 derivative (figs. D, H, L, 0, S and 30, 38, 44, 45). Since this last 

 primary division and the secondary division to form the sperma- 

 togenous cell and the sister sterile cell are to be found in the same 

 sporangium, it is evident that they are closely consecutive. The 

 complete development is extremely rapid; on May 3 only one- 

 celled stages were to be found, while on May 6, or sooner, the 

 pollination stage had been reached. Trees on a sunny hillside 

 shed the pollen at once; others retained it for ten days without 

 further development. The functioning antheridial cell is imbedded 

 in the cytoplasm of the primary cell, as shown above, and an in- 

 crease in the size of the pollen grain precedes mitosis of the former 

 cell. Evidently nutrition is a factor in determining the fate of 

 an antheridial cell; in other words, whether the first, second, or 

 third shall function as such. 



Degeneration 



In lenticular cells which contain a minimum of cytoplasm sur- 

 rounding the nucleus, the latter does not pass out of telophase 

 (fig. 26) ; the chromosomes contract, become globular, and finally 

 disintegrate as irregularly granular masses (figs. 20, 21, 43), or 

 accumulate at the periphery of the nucleus, giving it a vaginated 

 appearance (fig. 45). When these cells collapse, double darkly- 

 stained bands appear in cross-section. In Picea canadensis the 

 intine does not imbed these degenerating cells. The first primary 

 wall elongates as the pollen grain increases in diameter (figs. 37, 

 38, 50, 51); often it has the appearance of a third wall (fig. 50) 

 which is attached to the intine near the origin of the wings. The 

 disintegrating cell contents remain within the original walls; the 

 latter meanwhile become elongated and thickened. 



