262 



EXPERIMENTS WITH PLANTS 



of the branch, the supply of sap, of sunshine, of 

 elaborated food from the stem, and from the leaf in 

 whose axil the branch starts, etc. On pulling off the 

 bark of a tree (e. g., of a Pine or of an Oak) we find 

 under the bark, projecting from the wood, numerous 

 little incipient branches which have never been al- 

 lowed to develop (Fig. 145). 

 By splitting open the stem, 

 we may trace them inward 

 toward the heart through 

 several annular rings, thus 

 determining their age. Their 

 growth keeps pace with that 

 of the stem, but they thicken 

 scarcely at all ; in some cases 



145. Portion of trunk near a burl, show- the Y branch, CaUSmg the' ap- 

 ing latent buds beneath the bark, pearance familiar to us in 



"bird's-eye maple." In almost any good -sized tree we 

 may find such latent buds, as they are called, which 

 for several years have patiently awaited their chance 

 to develop. If now the tree be cut down, thus remov- 

 ing the fierce competition of the upper branches, they 

 spring up at once into wonderfully vigorous growth. 

 In this connection study cuttings and make such 

 experiments as are practicable. Do cuttings require a 

 light sandy soil in which air circulates freely? It has 

 been found that cutting a plant produces local fever 

 just as in an animal and an increased quantity of 



