A. St Clair Caporn 275 



This is particularly conceivable when some of the relations of the 

 streaked forms are considered. 



In maize certain 'splashed' purples are found; but "they are zygotic 

 variations which are not inherited, for their progeny are exactly like 

 the progeny of the dark purple seeds. Further, the patches are not in 

 a regular pattern nor does the selection of seeds of this nature have the 

 slightest tendency to fix the phenomenon as a separate character^" 

 Evidently, then, in wheat the streaked plants, many of which are 

 capable of being bred true, are of an entirely different kind. 



But there is another colour type in maize with which the appear- 

 ances of structural affinity are in some respects quite well developed, 

 though only in some. This type is known as ' particoloured,' the colour 

 being a very faint purple. If we imagine such diluted pigmentation 

 localised in one or two areas, and may be occasionally a little intensified 

 owing to this concentration, the ' streaked ' form results. In view of 

 certain similarities in the behaviour of their segregates which will now 

 be described, the visible differences between particoloureds and streakeds 

 are thus best likened to those between chemical allotropes. 



East and Hayes describe the occurrence of particoloureds in two 

 crosses ^ In the second they aye designated ' light purples,' not because 

 they are unlike particoloureds in outward appearance, but presumably 

 to emphasize an important difference in the gametic formulae. 



Where two factors, P and a colour factor C, are concerned in the 

 production of colour, it is held in the first cross the absence of C from 

 the combinations ccPP and ccPp does not prevent the formation 

 of a very small amount of colour. Hence the particoloureds. The 

 ratio of 9 purple : 3 particoloured : 4 non-coloured in the F2 genera- 

 tion lends support to the theory. Moreover, if allowance be made for 

 the fact that "particoloureds especially when non-starchy are not 

 always distinguishable fi-om whites," the agreement is fairly good. It 

 is better in ^3 if pure starchy groups be chosen. Again, ratios of 

 3 purple : 1 particoloured, 3 purple : 1 non-purple, and 3 particoloureds : 

 1 non-purple, as well as pure purples and particoloureds, occurred in 

 the ^3 generation. All these facts uphold the theory. But there is 

 clearly a weakness when it is stated" later that pure white races, 

 apparently devoid of any inhibitor of colour, may also have the gametic 

 formula cP. Moreover in yet another family, wherein it is alleged 



1 East and Hayes, p. 68. 



2 „ „ p. 67, Family (8 x 54) and p. 81, Family (60 x 54). 

 =* „ „ p. 102 (foot)— 103. 



