ARRANGEMENTS TO PROMOTE CROSSING. 



307 



turn. The stigmas in the centre of the flower are still folded together: as soon as 

 they begin to separate the anthers fall away from their filaments, and the five 

 mature outspread stigmas are surrounded only by the needle-shaped filaments 

 minus their anthers (fig. 291 a , the left-hand flower). The same thing happens in 

 some Saxifrages, of which Saxifraga rotundifolia (fig. 292) will serve as a type. 

 After the petals have unfolded, a peculiar action on the part of the stamens is to be 

 observed for several days. Each anther as it dehisces is raised up by its filament 

 into an erect position (see fig. 292 2 ), but remains in this position only for a short 

 time; it bends down again the next day or the next but one, resuming its original 

 position. The anther falls off, or if it remains as a shrivelled mass on the top of 

 the filament it has by this time lost all its pollen. All the stamens in succession 



Oft 



Fig 291. Completely dichogamous Flowers. 

 their dusty pollen. 1 and a nat. size; and somewhat magi 



undergo this rising and sinking. Not until all the pollen has disappeared do the 

 two short styles, which up till now have been folded together hke th, 

 of a pair of tongs (fig. 292*), separate from one another, and the.r st.gmas 

 capable of pollination (fig. 292 *). The Grass of Parnassus (Pamass^ p*u. 

 see fig 267 ' p. 249) as well as many Caryophyltace* (e.g. Ab* ~ SOen. 

 Ja) many Valerians (e.g. Valeria officinalis) and Tuhps (e.g. Tvkpa 

 SZTexhTbit the same course of development, especially the falhng away of 

 In Carohyllace* it often happens that the antherless filament* bend 



and become so hidden that the flower might 



The 







