i?8 
Journal of Agricultural Research 
Vol. XI, No. 4 
SUMMARY 
(1) Thirty-five genetic factors of the genus Pisum together with their 
common expressions, are listed and discussed in the present paper. 
The “presence and absence ” of these 35 factors are mainly responsible 
for 70 or more differential Pisum characters. 
(2) The modifying effects of the expression of one factor upon that 
of another, and the effects of external environmental conditions upon the 
expression of these factors, so far as known, are presented and discussed. 
(3) Data, involving many thousand P 2 generation progeny, indicate 
the factors A, B, (Ta), I, (Le), G, and R to be independently inherited— 
that is, not linked, unless the linkage is very loose. 
(4) Data for four linked groups are presented, three of which involve 
the factors mentioned under (3), and one of which the relations to the 
above seven are still undetermined. 
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