110 ORGANS AND FUNCTIONS OF PLANTS. 



the outer. When exposed to water, the inner swells 

 and bursts through the outer, forming a longish tube j 

 or bursts at two opposite points, as Amici observed in 

 the tree primrose. 



In the orchis and swallow wort 1 groups of plants, 

 the pollen, instead of being in grains, is found in a 

 solid mass, or several smaller masses united by an 

 elastic net- work. It is in all plants very inflammable; 

 and the peculiar odour of many flowers arises more 

 from it than from the petals. 



Needham formerly, and R. Brown lately, were led, 

 from observing the spontaneous motions of pollen in 

 water, to observe similar motions in inorganic sub- 

 stances, leading to the fanciful inference that all things 

 are full of life 2 . 



The Pistils and Seed-Organs. 



The pollen, when it arrives at maturity and bursts 

 from the cells of the anther, is shed upon the summit 

 of the pistil ; either from the stamens being near it j 

 or by the winds or insects, when they are at some dis- 

 tance on the same plants, as in the hazel, or on dif- 

 ferent plants, as in the hop. 



M. Lecoq, however, appears to have proved by ex- 

 periment, that fertile seeds may be produced in the 

 female hop plant without the intervention of the 

 male; and we have a similar example among animals 

 in aphides, of which the hop-fly is a species. 



Cl) In Latin, Asclepias. 

 <2) See the ALPHABET OF NATURAL PHILOSOPHY, or PHYSICS. 



