i6o 



I'LANT PROPAGATION 



ing a successful graft in such a case is increased if the 

 development of adventitious roots from the cion is en- 

 couraged, so that assimilation may correspond more 

 closel)' to a normal absorption of the cion. 



208. Graftage laws. — Daniel draws the following con- 

 clusions from certain of his experiments : 1, The relative 

 affinity or difference of functional capacities between 

 stock and cion at dififerent periods of the symbiosis 

 plays a very important role in the success, duration, 

 and biology of all grafts. 2, Environ- 

 ment, weather, etc., particularly sud- 

 den changes of environment, have com- 

 siderable reaction on the whole, a re- 

 action greater than in normal plants. 

 3, Various irregularities like diseases 

 result from faulty nutrition, due to 

 badly chosen grafts. 



209. Disease due to grafting. — A 

 study of grafts between various species 

 of Solanum (pepper, tomato, eggplant, 

 etc.) has led Daniel to conclude that 

 man)' of the physiological troubles of 

 plants commonly considered as dis- 

 eases are in reality due to the em- 

 ployment of antagonistic stocks and 

 cions. 



210. Grafts are of two classes,* anatomical 

 (grafts liy approach) and physiological (true) ; 

 the latter divided into two groups, ordinary 

 and mixed. In the ordinary the stock 

 is depri\ed entirely of its assimilating 

 apparatus (the green parts") and the cion of its 



absorbing parts (the roots). In the mixed graft proper tlie stock 

 may preserve part or all of its assimilating apparatus and the 

 cion part or all of its absorbing apparatus. In grafting by ap- 

 proach success is attained when the two plants grow together in 

 an enduring manner so that if separated a wound is formed. 

 The graft proper is said to succeed when, after having lived a 

 certain time on the stock, the cion produces fertile seeds. 



FIG. 136-^ 



YOUNG APPLE 



ROOT GRAFT 



This is student work 



*I. Daniel, Rev. Gen. Bat. 12, summarized in Ex. Sta. Record, Vol. 12, pp. 947,- 



