66 fHK VITAL FUNCJ^IONS. 



rounding the dark ring ; but after the fungi have 

 ceased to appear, the soil where they had grown 

 becomes darker, and the grass soon vegetates 

 again with peculiar vigour. When two adjacent 

 circles meet, and interfere with each other's pro- 

 gress, they not only do not cross each other, but 

 both circles are invariably obliterated between 

 the points of contact ; for the exhaustion occa- 

 sioned by each obstructs the progress of the 

 other, and both are starved. It would appear 

 that different species of fungi often require the 

 same kind of nutriment ; for, in cases of the in- 

 terference of a circle of mushrooms with another 

 of puff-balls, still the circles do not intersect one 

 another ; the exhaustion produced by the one 

 being equally detrimental to the growth of the 

 other, as if it had been occasioned by the pre- 

 vious vegetation of its own species. 



The only final cause we can assign for the 

 series of phenomena constituting the nutritive 

 functions of vegetables is the formation of cer- 

 tain organic products calculated to supply suste- 

 nance to a higher order of beings. The animal 

 kingdom is altogether dependent for its support, 

 and even existence, on the vegetable world. 

 Plants appear formed to bring together a certain 

 number of elements derived from the mineral 

 kingdom, in order to subject them to the opera- 

 tions of vital chemistry, a power too subtle for 

 human science to detect, or for human art to 



