180 



Gigantisni in Primula sinensis 



the floral habit of a plant may approach so nearly that of a giant as to 

 be recorded as a "doubtful giant" although, as shown by its progeny, 

 it is not pure for the giant character. 



TABLE VII. 



The Production of Giants by the Crossing of Noro-Giant Forms. 



I 190'j Snow Drift x Snow Kin;/^ 



1910 Fi= 22 plants: uo giants recorded 



selfed 2 plants 



1911 F„= ( 51/1 = 17 plants: no giants 

 51/2 = 10 plants of which 1 = (? giant) (51/2/1) 



selfed (? giant) and 4 non-giants 



1912 F-J-- 



II 



51/2/1 (fro7n {•> fiiatit) F«)= 7 plants, viz 

 51/1 {from noii-ijiant F.^) = H 

 51/fl ,, „ = 5 



51/il/ „ „ =14 



51/ir „ „ =27 



Snow Drift x White Queen Star (Normal) 

 9 plants, no giant 

 8/2/2 = 15 plants, uo giant 

 I 8/2/11 =1 plant non-giant 

 <8/2/2/ll = 9 plants, no giant 

 I 8/11 = 18 plants j 1 with giant flowers 

 t 1 ? giant 

 = 17 (?16) non-giant 



non-giant, 2 giant 



59 plants : none giant 



1 (?2) giant 



It must therefore be assumed that combinations of the factors A, B, C 

 other than the combination AABBCC may give rise to giant-like forms. 



The assumption which appears to fit the facts most nearly is as 

 follows : Of the three factors A, B, C two, but not any two, must be 

 present in the homozygous state for the definite manifestation of 

 gigantism. Provided that the plant have the constitution AABB, it may 

 exhibit well-marked gigantism even though the third factor C be present 

 in the heterozygous condition. Thus the three factorial combinations 

 AABBCC, AABBCc, AABBcC may all produce giant-like plants, albeit 

 the homozygous giant is recognizably more gigantic than the lietero- 

 zygous giants. 



The genetical behaviour of the "doubtful " giant 51/2/1 (Table VII, I) 

 demonstrates that it is not pure to gigantism. If there be ascribed to 

 it a con.stitution AABBCc, it should yield an F3 of 



AABBcC 

 AABBCc' 



1AABBCC:2 



lAABBcc. 



1 Snow King has flowers of fair size {xtelUitu type) and should perhaps be classed as a 

 semi-giant. 



