VEGETATIVE REPRODUCTION. 24 1 



the carpels may be united to form a single cmnpuund pistil. 

 This union is commonly brought about ( i ) by the actual 

 growing together of the parts in a very young stage, so that 

 the cells interlock and become partially or completely united; 

 or (2) the carpels develop, not as separate jjarts, but as a 

 ring of tissue growing up from the surface of the axis; or, 

 fs), a portion of each carpel develops separately, and later 

 these distinct parts may be lit'ted by the growth of the ring 

 of tissue beneath them (fig. 249). 



339. The union * of the carpels may be only at the base ; 

 or it may in\-olve the entire ovulary, lea\ing the st\les free : 



I'lG. 24-j, f'lG, 250. Fir,. 251. 



Fig. 249. — Pistil of white hellebore [Veratrum album) showing three carpels separate 



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

 Fig. 250. — Calyx and pistil of the manna ash {Fraxinus ornus\ sho\A-ing calyx leaves 



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



external e\"idence of theirnumber. Magnified several diam. — .After llerg and .Schmidt. 

 Fig. 2M. — Pistil of white potato hal\'ed transversely, showing two carpels united at 



center wliere their edges form a large placenta on whose surface the o\ules arise. 



Magnified se\"eral diam, — .After Kerner. 



or the -anion may be complete, with tlie excejition of the 

 stigmas, or it may in\-olve e\'en them (fig. 250), Union may 

 take place in such a way that the edge of each carpel meets 

 its fellow and the edges of neighboring carpels in the center 

 of the compound pistil (fig. 251). In this case the ovularv 



* This phrase may be used for convenience in all cases, even of those 

 pistils in which the carpels were at no time separate. 



