SECRETED FLUIDS. S5 



returning from the leaf, where it has been 

 acted upon by the air and hght, forming 

 new \Tood, is clearly the cause of the increase 

 of the vegetable body. But it is not so clear 

 hoNv the resinous, gummy or other secretions, 

 laid aside, as it were, in vessels, out of the 

 great line of circulation, can directly mini- 

 ster to the growth of the tree. I conceive 

 they may be in this respect analogous to ani- 

 mal fdt, a reservoir of nourishment whenever 

 its ordinary supplies are interrupted, as in 

 the winter, or ill seasons of great drought, 

 or of unusual cold. In such circumstances 

 the mucilaginous or saccharine secretions 

 especially, perhaps the most general of all, 

 may be absorbed into the vegetable constitu- 

 tion; just as fat is into the animal one, du- 

 ring the existence of any disease that inter- 

 rupts the ordinary supplies of food, or » 

 interferes with its due appropriation. It is 

 well known that such animals as sleep through 

 the winter, grow fat in the autumn and 

 awake very lean in the spring. Perhaps the 

 more recent layers of wood in a Plum- or 

 Cherry-tree, if they could be accurately exa- 

 mined, might be found to contain a greatei^ 



