CONIFERALES (PINACEAE) 



293 



The case of Sciadopitys (64, 175) presents an interesting variation, 

 but it is not so fundamental a difference as that shown by Sequoia. 

 The four tiers of the ])roembryo, as in Pinus, consist of open cell, 

 rosette, suspensor, and embryo tiers, but the last is represented by 



iJoii 





358 



Figs. 358-360. — Thuja occidoitalis: proembryo and early embryo; fig. 358, 

 mitoses giving rise to eight nuclei; the first walls appear in connection with this mitosis; 

 V, ventral canal nucleus; fig. 359, later stage, after the organization of tiers; fig. 360, 

 continued elongation of the suspensor; X425. — After Land (72). 



a loose group of cells, which Lawson (175) says become about six- 

 teen in number. The terminal cells of this group form the embryo, 

 those just above form a secondary suspensor, and there are still some 

 loose cells between the two suspensor regions (fig. 357). 



Among the Cupressineae the proembryos of Thuja (72) (figs, 

 358-360), Juniperus (95, 132) (figs. 361-363), and Libocedrus 

 (131) have been investigated. In all of them wall-formation occurs 



