l(j THE VITAL FUNCTIONS. 



tained, by the researches of Berzelius, is capable of 

 dissolving a very minute quantity of this dense and 

 hard substance. It is evident that, however small 

 this quantity may be, if it continue to accumulate 

 in the plant, it may in time constitute the whole 

 amount of that which is found to be so copiously 

 deposited on the surface, or collected in the interior 

 of many plants, such as the bamboo, and various 

 species of grasses. The small degree of solubility 

 of many substances thus required for the construc- 

 tion of the solid vegetable fabric, is, probably, one 

 of the reasons why plants require so large a supply 

 of water for their subsistence. 



^ 2. Absorption of Nutriment by Plants. 



The greater number of cellular plants absorb water 

 with nearly equal facility from every part of their 

 surface : this is the case with the AlgcE, for instance, 

 which are aquatic plants. In Lichens, on the other 

 hand, absorption takes place more partially ; but 

 the particular parts of the surface where it occurs 

 are not constantly the same, and appear to be 

 determined more by mechanical causes than by 

 any peculiarity of structure : some, however, are 

 found to be provided in certain parts of the surface 

 with stoinata, which De CandoUe supposes may 

 act as sucking orifices. Many mushrooms appear 

 to be capable of absorbing fluids from all parts of 

 their surface indiscriminately ; and some species, 

 again, are furnished at their base with a kind of 

 radical fibrils for that purpose. 



In plants having a vascvdar structure, which is 



