CONIFERALES 



327 



cleus moves to the peripheral end of the cell. Early in June, in the 

 Chicago region, archegonium initials are recognizable in Pinus 

 laricio; and in P. hanksiana they may be seen a week or 10 days 

 earlier. Within a week after the initial becomes recognizable, its 

 nucleus divides, giving rise to the central cell and the primary neck 

 cell (fig. 322). 



/*;-ir ',-"";''• H;^" 



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^ ;:.;-■ (,V',. 



m 



'I'v- '^S-^ 



B 



C 



D 



Fig. 322. — Pinus laricio: development of the archegonium; A, archegonium initial, 

 May 28; B, neck and central cells, June 2; C, two-celled neck and enlarged central cell, 

 June 18; D, mitosis cutting off ventral canal cell, June 21 ; X 104. — From Coulter and 

 Chamberlain, Morphology of Gymnos perms'^ (University of Chicago Press). 



After the primary neck cell is cut off, it soon divides, but it is 

 nearly a month before there is a division of the central cell. During 

 this period, the central cell enlarges immensely, and a very definite 

 archegonium jacket is formed, which plays for the central cell such 

 a role as the "endosperm jacket" plays for the female gametophyte. 

 With its enlargement, the central cell becomes very vacuolate, and, 

 besides the large vacuoles, a peculiar type of vacuole appears, the 

 "proteid vacuoles," which look so much like nuclei that Hof- 

 MEiSTER^s'' believed the eggs of gymnosperms differed from those of 

 angiosperms in being multinucleate. Hofmeister resented Stras- 



