200 



OUTLINES OF PLANT LIFE. 



may involve the entire ovulary, leaving the styles free; or 

 the union may be complete, with the exception of the 

 stigmas; or it may involve even them (figs. 155, 156). 



Fig 



Fin. 155. Fig. 156. Fig. 157. 



55. — Pistil of white hellebore {Verairutn album) showing three carpels separate 



above only. Magnified about 6 diam. — After Berg and Schmidt. 

 Fig. 156. — Calyx and pistil of the manna ash {Fraxiniis ornus) showing calyx leaves 



united at base and carpels united throughout, the slightly 2-lobed stigma only giving 



external evidence of their number. Magnifiedseveral diam.— After Berg and Schmidt. 

 Fig 157. — Pistil of white potato halved transversely, showing two carpels united at 



center where their edges form a large placenta on whose surface the ovules arise. 



Magnified several diam.— After Kerner. 



285. The ovulary. — The cavity of the ovulary is either 

 undivided or partitioned into as many chambers as there are 

 component carpels (fig. 157); or the normal number of 

 chambers in the ovulary may be in- 

 creased by outgrowths from the carpels 

 themselves (fig. 158). 



286. Ovules. — An ovule consists of a 

 central body, the spore case, in which the 

 megaspores are formed. In a few ovules 

 as many as 20 to 40 megaspores begin to 

 develop ; in most only one to four. Even 

 when several megaspores begin to form it 

 is rare for more than one to reach per- 

 fection ; the remainder disappear almost completely. The 

 megaspore never escapes from the spore case; for this reason 

 the megaspore looks more like a cavity in the ovule than like 



•^^^^ 



Fig. 15S. — A transverse 

 section of the capsule of 

 shepherd's pursed The 

 pistil consists of two 

 carpels, at whose united 

 edges two placentse are 

 formed carrying the 

 ovules (now seeds). The 

 partition from one pla- 

 centa to the other is an 

 outgrowth (false parti- 

 tion) and not part of the 

 carpel. Magnified about 

 6 diam.— After Bessey. 



