616 Mutations 



normal parents were in reality hybrids between 

 the type and the laciniated form, and simply 

 split according to Mendel's law. This hy- 

 pothesis is partly founded on general consider- 

 ations and partly on experiments made by my- 

 self with the cut-leaved celandine, previously 

 alluded to, which I crossed with the type. The 

 hybrids repeated the features of the species and 

 showed no signs of their internal hybrid con- 

 stitution. But the following year one-fourth 

 of their progeny returned to the cut-leaved 

 form. If the same thing has taken place in the 

 case of London's maples, but without their 

 hybrid origin being known, the result would 

 have been precisely what he observed. 



Broussonetia papyrifera dissecta originated 

 about 1830 at Lyons, and a second time in 1866 

 at Fontenay-aux-Boses. The cut-leaved hazel- 

 nuts, birches, beeches and others have mostly 

 been found in the wild state, as I have already 

 pointed out in a previous lecture. A similar 

 variety of the elder, Sambucus nigra laciniata, 

 and its near ally, Sambucus racemosa laciniata, 

 are often to be seen in our gardens. 'They have 

 been on record since 1886 and come true from 

 seed, but their exact origin seems to have been 

 forgotten. Cut-leaved walnuts have been known 

 since 1812; they come true from seed, but are 

 extremely liable to vicinism, a nuisance which is 



