Page:An introduction to physiological and systematical botany (1st edition).djvu/246

 216 all the agents above mentioned during its stay in the cellular substance of the leaf, and returned from thence impregnated with them into the bark, may prove the source of increase, and of peculiar secretions, in the vegetable frame. That portion of sap sent to the flower and fruit undergoes no less remarkable changes, for purposes to which those curious organs are devoted; nor is it returned from thence, as from the leaves, to answer any further end. The existence of those organs is still more temporary, and more absolutely limited to their own purposes, than even that of the leaves, from whose secretions theirs are very distinct.

But when we attempt to consider how the particular secretions of different species and tribes of plants are formed; how the same soil, the same atmosphere, should in a leaf of the vine or sorrel produce a wholesome acid, and in that of a spurge or manchineel a most virulent poison; how sweet and nutritious herbage should grow among the acrid crowfoot and aconite, we find ourselves totally unable to comprehend the existence of such wonderful powers in so small and