WHITE— STUDIES OF INHERITANCE IN PISUM. 489 



prisingly large in number, though each variety by itself differs from 

 all other varieties, as a rule, in comparatively few of them. In de- 

 scribing these characters and the experiments in connection with 

 them in Part II., they have been arranged in four groups — seed, 

 plant, floral and pod characters. In each of these groups, striking 

 hereditary differences are common. 



Thus, the seeds vary from 2 mm. to i cm. in diameter, with a 

 seed-coat color range from colorless through various shades of 

 green, reddish orange, brown, gray to deep purple. These colors 

 are further varied by color patterns of three types — marbHng, 

 striping and stippling. In plant characters, still more striking varia- 

 tions are apparent, such as differences in disease-resistance, in 

 height (38-300 cm.), in productiveness (3-4 small pods to varieties 

 with 50-150 pods), in stem color and shape, in leaf shape and color, 

 in number of pinnae per leaf, in the presence and absence of tendrils, 

 in internode length and number and in time of flowering. The 

 flozvers differ in size, color, shape, number per peduncle, in position 

 on the flowering axis and in time of pollen maturity. Three colors 

 of pods are known. Differences in pod length and breadth range 

 from about 10 by 1.7 cm. to 3 by 0.8 cm. (dry pods) with all de- 

 grees of intermediates between. Differences in shape, texture, 

 thickness, toughness, time of maturity for market (45 to 125 days 

 from time of planting) and in number of ovules per pod are striking. 



A large number of these variations, as the data presented under 

 Part II. disclose, yet remain to be experimentally studied. 



The Relation of Environment to the Material. 

 It is axiomatic that all organisms live in an environment of some 

 sort. Since the general acceptance of the Mendelian and genotype 

 conceptions of heredity, what part of the organism's characteristics 

 are due to environment and what part are due to heredity have be- 

 come very important questions for study and experimentation. The 

 Mendelian and genotypical conception that organisms are the ex- 

 pression of fixed and immutable factors or genes, which always 

 (barring mutations) give rise to the same character, provided the 

 environmental conditions remain constant, has led to a new concep- 

 tion of what constitutes a character. A character from this new 



