226 
MORPHOLOGY 
^' J%T * ' J * - '"- 
508 
509 
FIGS. 502-509. Development of embryo of Pinus: 502, fusion of male and female 
nuclei in the large egg; 503, four free nuclei (one in background) derived from fusion 
nucleus; 504, the four nuclei (two visible) at base of egg and dividing; 505, eight- 
nucleate stage (four nuclei visible); 506, the same a little further advanced; 507, next 
division, resulting in twelve cells in three tiers; 508, completed proembryo (four tiers of 
cells, uppermost open towards the general cytoplasm of the egg); 509, beginning of sus- 
pensor-formation (s), leaving within the egg the rosette cells (r), and thrusting out of it 
the four tip cells, which will form the embryo. After COULTER and CHAMBERLAIN. 
