G YMNOSPERM^E. 



401 



the female flower of the Gymnosperms. The only consider- 

 able departure from the plan of the flower, as here given, is 

 found in the order Gnetacece, which will be described further 



on. 



510. The ovule is at first a minute protuberance of 



-or- 



etn 



Fig. 297. A, longitudinal section of an ovule of Pinus Larico, taken from a 

 cone just opened ; c, the coat of the ovule, in si-ction ; ov, the body or " nucleus" of 

 the ovule ; this includes all the figure which is filled out, showing the cells ; em, the 

 young embryo sac. B, a similar section of the ovule of Abies peciinata, after the en- 

 trance of the pollen tube?, pt, into the corpuecula, cp, cp ; ov, the body or " nucleus'' 

 of the ovule the upper portion is cut away (the cells composing its tissue are not 

 shown); w, the wall of the embryo sac; en, endosperm in the enlarged embryo sac ; 

 cp, cp, two corpusculu ; n, the neck of one of the corpuscula ; pr, the first cells of 

 the pro-embryo. A X 150 ; B X 30. A after Hofmeister ; after Strasburger. 



small-celled tissue ; a little later a ring grows out from its 

 base, and rises as a sheath (the integument or coat), which 

 finally more or less completely closes it in ; in a few cases a 

 second integument forms outside of the first one. At a cer-< . 

 tain stage of its growth one of the interior cells of the ovule 

 grows larger than the others, and becomes the embryo sac 

 (em, Fig. 297, A) ; in it there arise numbers of free cells, 



