WHITE— STUDIES OF INHERITANCE IN PISUM. 501 



ing these sixteen years much has been accomplished through experi- 

 mental studies on peas and other organisms. Many comphcations 

 in the application of Mendel's law to data from these studies have 

 arisen, most of which have served to place the Mendelian concep- 

 tion of heredity on a still firmer foundation [see (6i)]. 



Among peas, over thirty-two different types of characters have 

 been experimentally studied, amounting in all to over 75 single char- 

 acteristics of Pisuni. In about half the cases, the knowledge gained 

 is somewhat fragmentary. In the other half, owing to the pains- 

 taking work of Mendel, Bateson, Vilmorin, Darbishire, Lock, Cor- 

 rens, Gregory, von Tschermak and others, the characters have been 

 put upon a factorial basis. In the list of characters studied which 

 follows, the factors are designated according to the presence and ab- 

 sence conception, small letters standing for absences. Where the 

 use of the letters for the factors given by the investigator of the 

 character concerned, is practicable, they have been retained. In 

 cases where this is inconsistent with the scheme of a complete anal- 

 ysis of the genus Pisum upon a factorial basis, new letters have been 

 substituted. In many cases these refer to adjectives descriptive of 

 the part they play in the formation of the character. 



In the case of some of the factors given in Tables I. and II., the 

 data hardly justify their consideration. However, since the data 

 upon which each factor determination is based are to be given in 

 the following pages, the writer justifies putting them in the tables 

 in the belief that further research concerning them will be more 

 quickly inspired. 



For the cause which this paper represents, it probably would be 

 better if all the crosses thus far made were given under each char- 

 acter description. Space at present, however, forbids this. So that 

 in the following pages, under the character description, will be given 

 the varieties studied, the results of the crosses in terms of dominance 

 and ratios, the factorial interpretation, the effect of the environ- 

 ment, if any, on the factorial expressions, and any remarks or ad- 

 verse criticisms. 



Reciprocal crosses in plants give the same results in all but a few 

 cases, and these few cases in Pisum are described. Otherwise the 

 reciprocal of a cross, although often made, is not specifically consid- 



