PROrEIiOaYNY AND PROTERAXDRY 



95 



Its style is two-cleft, the stigmas existing iipou the inner faces of the 

 branches, their outer faces being clothed with stifi" hairs pointing 

 nj)w;ir(l. It is obvious that until these style-branches separate, polli- 

 nation cannot take place. Before such separation occurs, the tip of the 

 style is, by elongation, slowly forced u]) through the tube of the anthers. 

 The anthers, with their contained pollen, are mature, and the pollen is, 

 by the stifi' hairs upon the backs of the style-branches, torn out from 

 its receptacles and exposed to such agencies of trans])()rtation as may 

 be prepared to act upon it. Cases are even known in which the tearing 

 out of the ])()l]cn in tliis way is cllVctcd by a spasmodic shortening 





Fig. 200. nichogamous flower of Milchrlla in first stage. 270. The same, in second stage. 271. 

 Dicliogamous flower of Vernoriia in first stage. 272. Style of same in second stage. 



of the stamens ni)on the instant of contact by a visiting insect, the 

 pollen being by the same process at once discharged iii)on tiie Ixidy of the 

 latter. After the removal of the j)ollcn, or after the (k-ath of such 

 grains as fail to be removed, the style-l)ranches .separate (Fig. '272) in 

 readiness to receive the pollen brought from .some other flower. This 

 method, or some modification of it. is very common among the Co7u- 

 positae, and illu.strates how the study of pollination serves to explain 

 many modifications of flower-structure otherwi.se inex])lieable, and why 

 the possession of tlic latter is reganh'd by the biologist as indicating a 

 higher stage of de\clo])ineiit. 



Dichogamy is very conmion among perfect aiieni()i)liil()us flowers, 



