THE COLOURFACTORS OF THE SEEDCOAT IN 
PHASEOLUS VULGARIS L. AND IN 
PH. MULTIFLORUS WILLD. 
by M. J. Sirks. 
(with 3 coloured plates). 
Researches into the various genetic factors, responsible for the 
different colours and patterns in the seedcoats of Phaseolus vul- 
garis L. and of Ph. multiflorus Willd. have already been published 
by several writers, These researches may be divided into two 
groups, considering the different ways, by which the results have 
been obtained. 
In the first place it will be possible to study these factors by 
means of artificial hybridizations between plants, belonging to 
different races of one of these species or by species-crossing and 
analizing the resulting F o-generations; if necessary the F3- and 
further generations may be cultivated as well. In this way the 
differences in genotypic constitutions of both parents may be found 
out, as papers of MENDEL (1865), TscHERMAK (1901, 1902, 1904, 
1912), EMERSON (1902, 1904, 1909 a and b), SHULL (1908), Snaw 
and Norton (1918), TjEeBBES and KOOIMAN (1919, 1921) and Kooı- 
MAN (1920) have shown. A great many genetic factors have been 
discovered by these authors The artificial hybridization of gar- 
denbeans however is not at all easy, as TSCHERMAK (1901, p. 706) 
first has pointed out; only a small percentage of crossings will 
give good results. And in the scarlet-runnerbean artificial crossing 
seems to be still more difficult. | 
Therefore another way may be gone with sufficient results: in 
Phaseolus spontaneous hybridization is rather frequent and its pro- 
ducts supply us with an excellent material for the study of the genetic 
factors. [n these cases one of the parents only,the motherplant, is known 
with certainty, but the fatherplant can be indicated frequently with more 
Genetica IV. 7 
