Page:An introduction to physiological and systematical botany (1st edition).djvu/74

 44 especially trees, differ from each other in the structure and disposition of them. Such observations, 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 experiments and observations, to be hereafter enlarged upon, prove also that air exists in the vegetable body, and must likewise be contained in appropriate vessels. Besides these, we know that plants are nourished and invigorated by water, which they readily absorb, and which is quickly conveyed through their