F. Keeble 177 



cross Giant Roj'al White x Crimson King the F-^ family consists of 

 semi-giants, and in yet other cases the F^ plants were not recorded 

 as showing giant habit of flower : whence it is to be inferred that if 

 they possessed any symptoms of gigantism those symptoms were too 

 slight to attract notice. 



The one case in which seed was obtained as a result of crossing 

 Giant White Queen Star, though it must be recorded, is open to 

 suspicion. The cross in question (Table III) was one between Giant 

 White Queen Star and its parent, the normal White Queen Star. Two 

 seeds only were obtained, and yielded plants of giant habit. It is 

 highly probable that they were the result of chance self-fertilization 

 of the giant, although it is to be noted that these F^ plants were sterile 

 both with their own pollen and that of normal White Queen Star. 



A superficial consideration of the differences which subsist between 

 the F^ generations might lead to the conclusion that two types of 

 gigantism occur in P. sinensis : one type in which the gigantism 

 behaves as a dominant character ; and the other in which it behaves 

 as a recessive. Such a conclusion is not open to objection on general, 

 theoretical grounds, and meets with support from the known facts of 

 gigantism in human beings. For as Gilford {op. cit.) shows, overgrowth 

 in man may be of a normal type or of a pathological nature. In the 

 former it is due to an exaggerated but normal development : in 

 the latter it would appear to be the consequence of the lack of a 

 growth-controlling factor. So in plants, excessive growth may be the 

 outcome of the presence of a factor for growth-acceleration (or for 

 inhibition of cell-division), or may be due to the absence of a factor 

 which in the normal plant controls and limits the amount of cell- 

 growth in the interests of the several organs or of the organism as 

 a whole. 



More careful examination of the results obtained with P. sinensis 

 serves to show, however, that to apply such an hypothesis to their 

 interpretation is certainly premature and probably unnecessary. 



Hence in the argument now to be developed it will be assumed 

 that there is but one type of gigantism in P. sinensis and that 

 gigantism is dominant to normality. The variable extent to which 

 the giant character manifests itself in F^ generations must therefore 

 be susceptible of explanation in terms of this hypothesis. 



An inspection of Table V shows that, as with the Fj generations, 

 so with F.2 generations, there is a remarkable lack of uniformity with 

 respect to the manifestation of gigantism. Thus the F„ and subsequent 



