524 Mutations 



branches. Most of them are crowned with 

 flowers in summer, which regularly succeed each 

 other, leaving behind them long spikes of young 

 fruits. The flowers are large and of a bright 

 yellow color, attracting immediate attention, 

 even from a distance. They open towards 

 evening, as the name indicates, and are pollin- 

 ated by humble-bees and moths. On bright days 

 their duration is confined to one evening, but 

 during cloudy weather they may still be found 

 open on the following morning. Contrary to 

 their congeners they are dependent on visiting 

 insects for pollination. 0. biennis and 0. 

 muricata have their stigmas in immediate con- 

 tact with the anthers within the flower-buds, and 

 as the anthers open in the morning preceding 

 the evening of the display of the petals, fecun- 

 dation is usually accomplished before the in- 

 sects are let in. But in 0. lamarckiana no 

 such self-fertilization takes place. The stigmas 

 are above the anthers in the bud, and as the 

 style increases in length at the time of the 

 opening of the corolla, they are elevated above 

 the anthers and do not receive the pollen. Or- 

 dinarily the flowers remained sterile if not vis- 

 ited by insects or pollinated by myself, although 

 rare instances of self-fertilization were seen. 



In falling off, the flowers leave behind them 

 a stout ovary with four cells and a large number 



