CHAP. V. FUNCTION OF REPRODUCTION. 263 



are at first close to the stigma, and the pistil is sud- 

 denly removed from them. 



But independently of any means which some species 

 employ for assisting the dispersion of the pollen and se- 

 curing its contact with the stigma, we find that the 

 mere conditions in which the flower is placed are often 

 such as are most likely to secure these results with- 

 out further contrivance. Thus, when the flower is 

 erect and the stamens are longer than the pistil, the 

 pollen on falling from the anthers is most likely to 

 come in contact with the stigma placed immediately 

 below them ; so also where the flower is pendent and 

 the stamens shorter than the pistil, the same effects 

 will be produced. In cases where the flower is erect 

 and the stigma stands higher than the anthers, there is 

 often a closer aggregation of the flowers as in the nu- 

 merous order Composite, so that the chances are greatly 

 increased whereby the pollen from one flower may be 

 brought into contact with the stigma of another, either 

 by the action of insects crawling over them or by the 

 mere agitation of the wind. These and a thousand 

 other instances might be adduced of a provision made 

 for securing the perfect success of an operation of so 

 much consequence to the preservation of the species. 



(259.) Protection of Pollen. It is further essential 

 that the pollen should be protected from the influence 

 of moisture ; and, consequently we find that aquatics, 

 as the water-lily (Nymphcea alba), elongate their flower- 

 stalks until the blossoms float upon the surface of the 

 water. In the water-soldier (Stratiotes aloides), water- 

 violet (Hottonia palustris], and others, the entire plants 

 float to the surface of the water during the period of flower- 

 ing, but live submerged at other times. In the Zostera 

 marina the flowers are arranged within a cavity filled 

 with air : and thus, although they are developed beneath 

 the surface, they are protected from the immediate 

 contact of the water. But of all instances that might 

 be mentioned, where the action of the pollen is secured 

 by some singularity of structure or contrivance, the 

 s 4 



