326 SEXUALITY OF VEGETABLES. CHAP. VI, 



inner side of the base of a stamefc ; it will im- 

 mediately spring forward till it strikes against the 

 pistil. Whence it is to be presumed that the effect 

 is often produced in the natural order of things, by 

 means of the feet or trunks of insects rummaging 

 the flower in quest of honey. 



From the Obs. 6. The economy of many of the aquatics 

 ofaquatics. seems also expressly intended to facilitate the process 

 of impregnation. Many plants of this class that 

 vegetate for the most part wholly immersed in water, 

 and often at a considerable depth, gradually begin 

 to elevate their stems as the season of flowering 

 advances when they at last rear their heads above 

 the surface of the water, and present their opening 

 blossoms to the sun, till the petals have begun to 

 fade, when they again gradually sink down to the 

 bottom to ripen and to sow their seeds. This very 

 peculiar economy may be exemplified ia the case 

 of Ruppia maritima, and several species of Pota- 

 mogeton, common in our ponds and ditches ; from 

 which we may fairly infer that the flowers rise thus 

 to the surface merely to give the pollen an opportu- 

 nity of reaching the stigma uninjured. 



But the most remarkable example of this kind 

 is that of the Valismria spiralis, a plant that grows 

 in the ditches of Italy. The plant is of the class 

 Dicecia, producing its fertile flowers on the extre- 

 mity of a long and slender stalk twisted spirally 

 like a cork-screw, which uncoiling of its own ac- 

 cord, about the time of the opening of the blossom, 



