18 STRUCTURE AND FUNCTIONS 



the straw ; the stems of mushrooms, fungi, &c. 

 are termed the stalk, and the stem of the straw- 

 berry is termed a runner, all of them being ap- 

 propriately described from the appearance each 

 presents. 



The functions performed by the stem are lit- 

 tle more than that of conveying to the different 

 parts of the plant the liquids absorbed by the 

 spongelets of the root. It is somewhat porous, 

 and evaporation of the useless moisture of the 

 plant takes place to some extent on its surface, 

 but compared in this respect with the leaves, 

 its office is unimportant. It consists in all 

 cases of cellular tissue, containing albumen, 

 with a large portion of the earthy and alkaline 

 matter absorbed by the roots, and it partakes 

 largely also of the character of the plant itself 

 in its ultimate analysis, but frequently contains 

 a deposite of resinous or oleaginous matter, dif- 

 fering widely from the products of the other 

 parts of the plant. It possesses the property 

 of throwing out fibres and spongelets under fa- 

 vourable circumstances, and this mode is one 

 of the most common means employed for the 

 propagation of particular shrubs. 



The leaves of plants are the next subject for 

 consideration, and the important offices they 

 perform in the nutrition of all plants will merit 

 a careful investigation. 



Nature, in all her operations, as far as hu- 

 man knowledge extends, is perfect. Sufficient 

 means are always employed to obtain a given 

 result; and hence we may justly infer that 

 leaves from their immense number and from 



