164 



ARCHEGONIATES. 



The development of the archegonium is the same as in the lower 

 gymnosperms. The ventral canal-cell is separated from the egg merely 

 by a plasma membrane, which is formed by the connecting fibers, as 

 is usual in the higher plants. It persists for a short time only. In 



s-n. 



D 



a,.c. 



sl.c. 



FIG. 68. Pollen grain, end of pollen tube, and fusion nucleus of Pinus stroiius. (After Ferguson.) 



A, mature pollen grain. /' and/', remains of first and second prothallial cells; a. c., antheridial cell. 



B, pollen grain in which antheridial cell has divided. .c., generative cell ; st.c., stalk cell. 



C, distal end of pollen tube which is pushing between neck-cells of archegonium ; the male nuclei (s.n.) 



are of unequal size, v.n., tube nucleus ; st.c., stalk cell ; i.e., cytoplasm of generative cell. 



D, first mitosis following fecundation. The spindle is formed, but the male and female chromatin 



spirems are still separate and distinct. 



Pinus strobus, according to Ferguson, there are probably instances 

 in which the nucleus of this cell is not reconstructed, and this may be 

 true also in other genera and species. 



