342 THE GERM-PL.\SM 



occurred in this case, the niDubcr of ida^its of Cytisiis adajni must 

 be as large as that of the two ancestral species taken together ; 

 for, as far as we know, a process of reducing division only 

 occurs in the formation of sexual cells. The correctness of my 

 ?fssumption can therefore be controlled by observation. 



It is hardly conceivable that two young plant-cells could, 

 without fusing, have formed the growing point of the hybrid- 

 shoot ; for probably only one of these cells could have performed 

 the function of an apical cell, and consequently tlie hereditary 

 influence of the other could not have extended to countless 

 daughter-shoots, as was actually the case. In the course of 

 growth, every cell below the apical cell must necessarily have 

 gradually come to be situated further away from the growing- 

 point. Such an intimate combination of characters as actually 

 occurred could not have been effected in this way. 



I am therefore inclined to suppose that the unusual phe- 

 nomena exhibited by Cytisiis adanii were due to an abnormal 

 kind of amphimixis, so that the idants of both species were 

 combined in the apical cell of the first shoot ; but that in the 

 subsequent cell-divisions an unequal distribution of the two 

 kinds of parental idants amongst the daughter-nuclei took 

 place, thus producing the variations in the combination of the 

 characters. 



Such an unequal distribution of the superabundant idants 

 might also occasionally occur in an apical cell itself. This proc- 

 ess may, moreover, be connected with the frequent complete 

 reversion of an entire branch to one of the ancestral species, as 

 well as with the fact that a modification tending to make 

 the parental characters more and more distinct has occurred in the 

 course of time in many examples of hybrids. Shortly after the 

 first appearance of the Cytisus-hyhndj the colour of all the flowers 

 was a dingy-red, — that is, an intimate mixture of the two ancestral 

 colours, yellow and purple ; but by degrees this mixture became 

 less perfect, until eventually pure yellow and pure purple flowers, 

 and even entire clusters of flowers and entire branches possessing 

 almost the pure character of one or other of the parent-species, 



its centrosome, which has already become doubled by division. The 

 nuclei then come to be situated close together, the centrosomes uniting in 

 pairs, just as in the ordinary process of amphimixis; and finally the two 

 nuclei fuse together completely. A spindle of division is then formed, and 

 several divisions follow close after one another. 



