Flowers. 



179 



is readily dispersed from flower to flower at any depth. 



In the case of Vallisneria spiralis 



(see Figs. 95-96) the pistillate 



flowers rise to the surface on 



slender stems. The staminate 



flowers, which are formed under 



the water, break loose from their 



stems and float on the surface, the fig- 94- 



calyx consisting of boat-shaped Fruiting Scale or Carpel from a 



sepals which buoy the stamens rffo'rs'ow^g ^rvut"; 



above the surface, and allow them B, diagram of a longitudinal 



n ^ 1 • t 11 --I-11 . section of ^, seen from the side. 



to float high and dry. The Sta- ,„ niicropyle; «, embryo sac. 



mens bend outward beyond the rim a, after bessey ; b, after Cald- 



of the calyx, and when the stami- 

 nate and pistillate flowers 

 are brought together by the 

 wind or currents of water, 

 the anthers come in contact 

 with the stigmas and effect 

 their pollination. The stem 

 which bears the pistillate 

 flowers then coils itself spi- 

 rally and draws the flower 

 to the bottom of the water, 

 where the seeds may ma- 

 ture undisturbed. 



129. Adaptations to In- 

 sects. — The most wonder- 

 ful modifications of flowers 

 found in those forms 



are 



Fig. 95. 

 Vallisneria spiralis. The plant on the left 

 bears staminate flowers which are break- i . , i , i , 



ing away and rising to the surface. The whlch are adapted tO CrOSS 

 plant on the right bears a pistillate flower pollination by means of in- 

 rising on a long stem to the surface. — 



After KEENER. 



sects. These have had to 



