THE PHENOMENA OF REVERSION 34 1 



Cytisus adami was obtained from a young bud on a portion 

 of the bark of Cytisus purpurea, which was grafted into the 

 stem of C. laburnum. This bud developed into a shoot which 

 exhibited an intimate combination of the parental characters. 

 The shoot was afterwards propagated, and the plants raised 

 from it exhibited ' reversions to both of the parental forms,* as 

 well as dingv-red, /.<?., mixed blossoms, so that the pure characters 

 of the parents were displayed in more or less extensive regions 

 of the hybrid. 



From a theoretical point of view, it can obviously be granted 

 that a mongrel-plant may originate by contact of the living 

 tissues of the parents, only if the transformation of the rudiment 

 of an existing shoot is out of the question, and if the rudiment 

 then appears for the first time. An existing dormant bud, which 

 contains all parts of the shoot, cannot become modified as 

 regards the idioplasm which it contains by the stock of another 

 species which nourishes it : its apical cells, from which further 

 grow'th proceeds, cannot receive a supply of extraneous idioplasm 

 from the supporting stock ; for the nuclear rods alone contain 

 idioplasm, and this is a solid substance, and can only undergo 

 combination by the fusion of tw^o cells and their nuclei. It is 

 therefore also worthy of notice that Adams did not observe that a 

 hybrid w-as developed from the single dormant bud which was from 

 the first present on the graft, but that the hybrid arose from one 

 of the later buds which were formed in the second year ; moreover, 

 only one, and not all, of these buds produced bud-hybrids. The 

 formation of this single hybrid-bud must have been regulated by 

 an unusual and accidental occurrence, for all efforts to produce the 

 hybrid a second time have so far been in vain. This accidental 

 occurrence must have been that the cambium-cells of the two 

 species came to lie close together, so that they could both enter 

 the same bud arising from the cambium. Botanists must 

 decide whether two cambium-cells, belonging to different species, 

 can conceivably become united into one by a process of con- 

 jugation similar to that which occurs in the union of the male 

 and female cells in fertilisation, and whether the foundation may 

 in this way be laid for a new growing point.* If such a process 



* K fusion of nuclei, apart from that seen in the process of fertilisation, 

 actually occurs in plants in the case of the embryo-sac. Guignard {loc. 

 cit.) describes this process in detail as follows: — The 'upper and lower 

 pole-nuclei ' of the embryo-sac approach one another, each accompanied by 



