44 OF THE SAP-VESSELS. 



especially trees, differ from each other in the 

 structure and disposition of them. Such ob- 

 servations, however, if pursued no further, 

 lead but a little way towards a knowledge of 

 the wonderful physiology of vegetables. 



In our 2d chapter, mention is made of the 

 general cellular and vascular texture of plants; 

 we must now be a little more particular in our 

 inquiries. 



That plants contain various substances, as 

 sugar, gum, acids, odoriferous fluids and 

 others, to which their various flavours and 

 qualities are owing, is familiar to every one ; 

 and a little reflection will satisfy us that such 

 substances must each be lodged in proper 

 cells and vessels to be kept distinct from each 

 other. They are extracted, or secreted, from 

 the common juice of the plant, and called its 

 peculiar or secreted fluids. Various experi- 

 ments and observations, to be hereafter en- 

 larged upon, prove also that air exists in the 

 vegetable body, and must likewise be con- 

 tained in appropriate vessels. Besides these, 

 we know that plants are nourished and invir 

 gorated by water, which they readily absorb, 

 and which is quickly conveyed through their 



