gtmnosperm^. 



401 



the female flower of the Gymnospei'ms. The only consider- 

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

 found in the order Gnetacem, which will bo described further 



on. 



510. 



-The ovule is at first a minute protuberance of 



em 



Fig. 297. — A^ longitudinal section of an ovule of Finns Larico, taken firora a 

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

 the ovule : this includes all the. figure which is filled itut. showina; the cells ; fm, th ; 

 young embryo sac. B, a similar section of the ovule of Abies p'ieiinata^ after th •. en- 

 trance of the pollen lubes, pt, into the corpnscula, 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 corpuscula ; n, the neck of one of the corpuscula ; ;»•, the first cells of 

 the pro-embryo. >1 X 150 ; .B X W.—A after Hofmeister ; B 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. 397, A) ; va. it there arise numbers of free cells, 



