CONITERALES (PINACEAE) 



291 



which is the plate or group of proembryonic cells remaining within 

 the egg and mediating between the food supply of the egg and the 

 suspensor. The size and generally active appearance of the four 

 uppermost nuclei, exposed to the cytoplasm of the egg, indicate that 

 they must remain functional for some time. 



This account of the proembryo of Pinus probably applies equally 

 well to all the Abietineae, although the account is not full for any 

 other genera except Picea (79) and Pseudoisuga (156). The other 



IP O O 



Figs. 353-355. — Proembryo of Taxodineae: fig. 353, Taxodium distickum, sixteen- 

 celled embryo in three tiers, six cells in rosette, six in suspensor, and four below; X 280; 

 after Cokee (76); fig. 354, somewhat later stage of same; X37S; after Arnoldi (64); 

 fig- 355> Cunninghamia sinensis, proembryo of three tiers of cells; X145; after 

 MiYAKE (147). 



tribes have received the chief attention recently, and deserve some 

 separate mention. 



Among the Taxodineae, the proembryo of Cryptomeria (64, 93), 

 Taxodium (64, 76), Sciadopitys (64, 175), Sequoia (92), and Cunning- 

 hamia (147, 180) have been investigated (figs. 353-355). In all of them, 

 with the exception of Sequoia, wall-formation occurs at the appearance 

 of the eight-nucleate stage, but there is considerable variation in the 

 passage of free nuclei to the base of the egg, even in the same form. 

 For example, in Cryptomeria one observer (64) reports that the fusion 

 nucleus passes to the bottom of the egg, while another observer (93) 



