CAUSES OF BARRENNESS, &C. 169 



shoot, at the point where a perfect fruit, in other 

 circumstances, would have been formed. 



Notwithstanding this irregularity, and intermix- 

 ture of distinct organs in the growth, (which may be 

 easily traced to be effects of accident, or extreme cul- 

 tivation,) it has furnished some physiologists with an 

 idea that such exhibitions indicate the true reason 

 why one tree is prolific and another barren : why one 

 tree shall every year be covered with blossoms, and 

 another of the same kind present nothing but leaves. 

 The sexual organs of plants they assume have no 

 positive identity ; but are only modifications of the 

 previously existing members which compose the 

 stem, and which are resolvable, either into leaf or 

 flower-buds, as circumstances govern. 



That there is some corresponding analogy between 

 the members of a stem and those of a flower, may be 

 admitted. We have only to refer to the doctrine of 

 the old botanists for confirmation. They declared 

 that the calyx was the termination of the outer bark 

 the corolla, that of the liber the stamens rose 

 from the wood and the pistillum, &c., from the 

 pith. These old ideas have, however, become obso- 

 lete ; and instead of them we are now taught, that 

 " the pistillum is either the modification of a single 

 leaf, or of one or more whorls of modified leaves," 

 and " that in the course of the advance of it to ma- 

 turity, many alterations take place in consequence of 

 abortion, non-development, obliteration, and union 

 of parts." De Cand. 



