564 WHITE— STUDIES OF INHERITANCE IN PISUM. 



Plant A, 27 : 20 emerald, 

 Plant B, 23 : 21 emerald. 



Actual, 50 : 41 



Calculated, 51.1 : 39.8 



In F3 6 F2 glaucous plants gave in one case all glaucous, in 5 

 cases both glaucous and emerald. Of 3 Fo emeralds tested in F3, 

 only emerald progeny resulted. 



Interpretation. 



The above data show that two factors are involved in the inheri- 

 tance of bloom ; in the absence of either or both, the plant is 

 emerald. No emeralds have been obtained as yet in which both 

 factors for bloom are absent. Regarded thus, in respect to bloom 

 and its absence, varieties of peas with bloom are BIBIWW, while 

 emeralds may be either blblww, BlBlww or blblWW. Emeralds of 

 the first type should be obtained as segregates. 



15. Productiveness. 



Productiveness is to be regarded as a composite character or one 

 made up of a very large number of other characters. Length of 

 vine, number of internodes, number of pods per single peduncle, 

 number of pods per plant, length of pods, number of pea ovules 

 per pod, number of peas matured per pod are a few of the heredi- 

 tary characters, the combined results of which are called productive- 

 ness. In addition to these there are a host of environmental condi- 

 tions which either raise or lower the hereditary productivity of a 

 variety. For a scientific study of the heredity of productiveness, 

 it is necessary to eliminate as nearly as possible variation caused by 

 environment, and this is most easily accomplished by growing the 

 varieties to be studied and their hybrids under as near as practicable, 

 one set of conditions. A study of this character under these condi- 

 tions, so far as I am aware, has not yet been published. 



Varieties of peas, as well known, differ remarkably in the aver- 

 age number of pods they bear, and these variations are governed, as 

 usually studied, quite as much by environment as by heredity. Such 

 early varieties as Morning Star, Excelsior, Velocity and others do 



