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 proembryo, as in Pinus, consist of open cell, 

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



368 



Figs. 358-360. — Thuja occidentalis: 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; X42S. — ^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 Lihocedrus 

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



