SPERMATOPHYTA 



351 



Fig. 300. Early embryogeny of Pinus monophylla. A, 2-nucleate proembryo; B, 4- 

 nucleate stage; C, two of the four nuclei at base of egg; D, 8-celled proembryo; E, three 

 tiers of four cells each; F, four tiers of four cells each; G, cells of suspensor tier elongating; 

 H, later stage of Pinus banksiana, the four proembryos separating; r, rosette cells; s, 

 primary suspensor cells; ei, 62, es, secondary suspensor cells; A and B, X75; C to G, X 125; 

 H, XQO. {H, after Buchholz.) 



