WEISMANN'S THEORY OF THE GERMPLASM 71 



not adapted to each other, no attempt at union 

 occurs, and the grafted twig speedily perishes ; 

 sometimes even the stem dies, as if it had been 

 poisoned by the graft. In other cases the dis- 

 harmony is not shown so strongly. The twig and 

 the stem begin to unite, but. sooner or later, dis- 

 turbances occur, and complete destruction results. 

 According to Vochting, in the case of some Cruci- 

 ferce the disturbances are as follows : the twig 

 begins to form roots at its lower end, and these 

 QTOW into the stem of the host. Through them the 



O o 



twig uses as food the juices and salts of the stem, 

 refusing to unite with the stem so as to form a 

 single individual. As Vochting says, this forma- 

 tion of roots simply is an attempt on the part of 

 the twig to complete its own individuality. Instead 

 of growing into corporate union with the stem, the 

 twig attempts to become a parasite upon it. A 

 further consequence often is, that the stem, too, 

 begins to respond to the unadaptive stranger's in- 

 fluence. Thus, when Vochting grafted a Rhipsalis 

 paradoxa on an Opuntia laJbouretiana, he found 

 that round the roots of the graft the tissues of the 

 host threw out a protective sheath of cork, or 

 turned in places to a gelatinous mass. 



In some cases experimenters have overcome dis- 

 harmony between two species, A and B, by making 

 use of a third species, C, with a vegetative affinity 

 for both A and B. Thus, an intermediary between 

 the two disharmonic forms is made, and by such an 

 arrangement a single functional individual is pro- 

 duced from pieces of three different species. Thus, 



