152 



GENERAL BIOLOGY 



the embryo itself is the new sporophyte. If this seem con- 

 fusing, the way to make it clear is to inquire what is the 



origin of each part. To learn 

 ^vhat is gametophyte, learn what 

 has developed from the spore. 



The pine and the violet repre- 

 sent the two chief groups of 

 seed plants, whose most salient 

 characters are found in flower 

 and fruit. The gymnosperms 

 (gymnos, naked and sperma 

 seed) bear the ovules, and later 

 the seeds, uncovered upon the 

 surface of the scales. The an- 

 giosperms {angios, a closed ves- 

 sel, and sperma seed) have the 

 ovules (or the seeds) included 

 within the closed pistil. 



Reproduction in the violet. — 

 Many signs of specialization are 

 evident in such flowers as vio- 

 lets. Their general structure 

 has already been discussed and 

 illustrated in Chapter I. We 

 are here concerned only with the 

 phenomena that lead directly to 

 seed development . 



The microspore (pollen) de- 

 velops a male gametophyte of 

 but two cells, and one of these 

 is very small (fig. 976) ; but from 



Fig. 97. The microspores of the 



t'^ poUen-t .tel°^"we't it are derived the two sperm nu- 

 r>VetSopSt'°onrj,o'iie1; clei. The other develops when 



tube in sugar solution; c, after 

 15 minutes; e, after an hour; 

 one sperm nucleus shows in /. 



The other develops 

 it is carried to the moist stig- 

 matic surface of the violet pistil, 



