Oenothera Scintillans. 383 



The development of the anthers and the pollen is to a 

 high degree dependent on external conditions. The pol- 

 len is sometimes plentiful, sometimes scanty, and at 

 other times entirely absent. These variations occur on 

 one and the same plant and seem to depend chiefly on 

 the temperature, inasmuch as the anthers degenerate 

 under the influence of hot weather. It is in consequence 

 of this circumstance that I have lost many fruits by en- 

 closing flowers in parchment bags (to insure pure self- 

 fertilization) in the full sunlight. 



Fig. 82. Oenothera scintillans. A rosette ot radical 

 leaves, at the end of June. 



The annual plants are only very slightly branched, 

 and begin to flower when they are only Yo meter high. 

 The lateral branches spring from just underneath the 

 flowering zone, and on them isolated flowers appear 

 towards the end of September or even later. Biennial 

 plants are usually more branched, and if the heart of the 

 rosette happens to have frozen in the winter a circlet of 



