F. Keeble 186 



AABBcc X AABBCC 

 yields i^i = AABBCc 



F2, of 3 giant and giant-like forms : 1 non-giant 

 = in 18 plants : 13'5 giant : 4-5 non-giant 

 as compared with 13 ,, : 5 „ found (Table V). 



In supposing that plants which, in F-^, were ranked as semi-giants 

 are liable to be classed with giants in F„ no violence is done to 

 probability; for in the first place the judgment is a rough judgment 

 and in the second place the habit of inflorescence in F^ is apt to be free, 

 and the flowers borne in such an inflorescence are less likely either to 

 appear or to be gigantic than those which are borne on a more 

 massive flower-stalk. Indeed the records of the behaviour in sub- 

 sequent generations of plants recorded as giants show that not all 

 plants to which gigantism is ascribed with confidence prove to be pure 

 to that character. 



Finally with respect to the Mendelian phenomena of gigantism it 

 appears reasonable to conclude that gigantism in P. sineiwis depends 

 for its full expression on the simultaneous presence of three factors : 

 that pure giants are homozygous for these factors ; that giant-like 

 forms occur when the plant is heterozygous for the C factor ; and that 

 an intergrading series of semi-giant races occurs in which the grades 

 are represented by appropriate combinations of factors and their 

 " absences." 



Theoretical Considerations. 



Numerous considerations, some of no small interest and importance, 

 arise out of the results which have been described in the previous 

 sections ; but of these considerations only few can be discussed in the 

 present paper. 



First among them is the question concerning the origination of 

 Giant White Queen Star. Is the fact that it arose in course of 

 "selection" of flowers with supernumerary petals a mere coincidence or 

 did the selection process play any part in the liberation of the giant ? 

 If the hypothesis on the nature of fluctuation (see p. 184) be accepted it 

 is evidently susceptible of application in the present case. For a form 

 of P. sinensis of the type of constitution AaBbcc though, for lack of 

 the C factor, it may not produce giants, may produce gametes of various 

 constitutions and these in turn combining in the various ways open to 



