2S6 



MORPHOLOGY OF GYMNOSPERMS 



solitary in Taxodium {'j6), three or four in Crypiomeria (93), and 

 five or six in Sequoia (92) ; and among the Cupressineae, Thuja (86) 

 occasionally has two or three mother cells, and Libocedrus (131) one 

 to three. That the number of mother cells may be quite variable 

 is shown by the case of Cunninghamia, in which one observer (64) 

 reported several mother cells developing embryo sacs, and another 



Fig. 280. — Firms Laricio: longitudinal section of an ovule on June i, with mega- 

 spore mother cell in the center, surrounded by a region of more or less modified cells; 

 nucleus of mother cell in prophase of reduction division; Xsoo. 



(147, 180) reported a solitary mother cell. The season for the recog- 

 nition and functioning of mother cells has been mentioned, ranging 

 throughout all the spring months for different latitudes, but there is no 

 clear evidence whether in any case the megasporangium passes the 

 winter in the mother cell stage, as is often true of the microsporangium. 

 A well-marked feature of the Pinaceae is the development of a 

 more or less extensive zone of nutritive cells about the enlarging 



