106 SIRKS, THE COLOURFACTORS OF THE SEEDCOAT IN PHASEOLUS 
segregations, TSCHERMAK has suggested the existence of two colour- 
factors besides the groundfactor A,, that is necessary for the 
appearance of colour in beans, viz. B causing a violet colouring, 
and C colouring in coöperation with A alone the seedcoat with a 
yellowish brown colour; B and C together with A, would give a 
black seedcoat. The factor B according to TSCHERMAK, may be 
divided into two components B, and Bo; B,° Bg as also By bo 
giving a violet colour, by By a red one. 
EMERSON has, in the footsteps of SHULL, supposed four colour- 
changing factors to be present in various races of beans: O changing 
yellow into orange-brown, D giving darkbrown and B, changing 
darkbrown into black; R a factor causing a red colour, would be 
hypostatic to orange-brown, this orange-brown ‘to the other 
colours a.s.o. 
In later years KAJANUs (1914) has given some results of spon- 
taneous crossings, without pointing out the factors concerned 
therein; LUNDBERG and AAKERMAN (1917) however did so in foun- 
ding G as the factor for a yellowish-brown colour, and C as that 
for a chocolate-coloured seedcoat; their coöperation results into 
darkbrown, the absence of both of them yellowish white. Then 
ccgg = yellowish white, ccGG= yellowish brown, CC ¢ 6 = 
chocolate and CCGG— darkbrown. Both these factors would 
segregate independently with a segregation in Fo of 9:3:3:1. 
Researches on a large scale at the Massachusetts agricultural 
experiment station have enabled SHAW and Norton (1918) to 
discover a many colourfactors: besides P, the groundfactor for 
pigmentation, two modifying factors M and MI would give rise to 
two types of colouring; one, M, being present in the beans with 
yellow-black colours, the other M! in those of the red series. In 
the authors opinion these factors are enzymes, and necessary for 
the existence of colours. Further the writers have found factors 
for black (G), for coffeebrown (F), for yellow (C), for darkred (E), 
lightred (D) and in one race (Creaseback) still another black 
factor X. 
The papers of TJEBBES and KOOIMAN have also unveiled some 
colourfactors, present in various races of gardenbeans. In their 
first paper (1919) the cross between a common yellow-brown 
race and a violet-striped one was studied: the genotypic formula of 
