March 21st, 1916.] PROCEEDINGS. xxxv 



well-known graft hybrid, Cytisus Adami originated in 1825 by- 

 budding Cytisus purpurens on Cytisus laburnum, the yellow 

 laburnum. In this case the main bud perished, but at its side 

 an adventitious bud was formed and the shoot which developed 

 from it bore foliage of a size intermediate between those of its 

 parents. The inflorescence of this so-called purple laburnum 

 was also intermediate in size, and the flowers in colour a mixture 

 of yellow and purple. While in the case of this "graft hybrid " 

 the majority of the branches bore foliage and flowers of the 

 intermediate kind, known as Cytisus Adami, reversions to both 

 the yellow Laburnum and the purple Cytisus are frequent, and, 

 in some cases, even portions of a leaf or flower may revert to 

 one of the parents. 



Recently H. Winkler has produced a number of similar 

 " hybrids " by grafting shoots of the tomato upon the black 

 nightshade, and vice versa. When a firm union of stock and 

 graft had taken place the plant was cut down to the region of 

 the graft, and then numerous adventitious buds made their 

 appearance from the region at which the two plants were united. 

 In this way five distinct forms of shoots were obtained, all of 

 them intermediate between stock and scion, but some leaning 

 more to the tomato, others to the nightshade. Reversions to 

 the two parents also commonly occur. 



Macfarlane, in his careful description of Cytisus Adami, 

 had already pointed out (1892) that this plant seemed to be 

 " wrapped round by an epidermis of Cytisus purpurens " as its 

 external features partook so closely to the nature of this latter 

 species, and it is singularly noticeable that in most of Winkler's 

 "graft hybrids" the outer layers showed a predominance of the 

 characters of one of the parents. A closer examination has 

 revealed in Cytisus Adami that the outermost layer of cells of 

 all organs of the plant show in their most detailed characters 

 all the features of the purple Cytisus, while the inner core of 

 the plant seems to consist exclusively of cells of the yellow 

 laburnum. Of Winkler's "hybrids " one seems to be covered 

 by one layer of cells of the tomato, and another by two layers 



