ADJUSTMENT TO TEMPERATURE 



123 



Flowers usually open before or upon the maturity of anthers 

 or of stigma, but sometimes they remain completely or partly 

 closed and are called cleistogamous. Homogamous flowers, which 

 open, may have the anthers and stigma so placed that self-pollina- 

 tion is impossible, or these parts may be contiguous in such fashion 



Fig. 31. Dichogamy in the firowecd, Chnmcenerium angustijolium, in 

 which the anthers mature before the stigma. (After Kernel-. j 



that self-pollination may occur. Flowers that may be self-polli- 

 nated sometimes have the stamens, or the stamens and the styles, 

 in two or three sets of different lengths, in a measure decreasing 

 the disadvantage of self-pollination. 



Experiment 40. Grouping of stamens and pistils. Note the relations 

 of stamens and pistils in various flowers of the spring flora. Make 



