INHERITANCE STUDIES IN PISUM 



I. Inhekitance of Cotyledon Coloe 1 



DR. ORLAND E. WHITE 

 Curator or Plant Breeding, Brooklyn Botanic Garden 



Introduction 



Modern students of genetics such as Baur, East, Mor- 

 gan, Emerson, and others classify all variations in ani- 

 mals and plants into three general categories on the as- 

 sumption that organisms are made up of unit factors, in 

 the same way that a chemist thinks of rocks and minerals 

 as being composed of elements. These three categories 

 of variation are : 



1. Variation resulting from changes in environment. 



2. Variation due to ''loss" or "gain" of new factors 

 through crossing. 



3. Variation due to mutation. 



The Problem 



The present paper has to do largely with data on vari- 

 ations in Pisum belonging to the first and second cate- 

 gories mentioned above. An attempt is being made defi- 

 nitely to work out the Mendelian or factorial constitution 

 of the genus Pisum with reference to all those characters 

 by which its few species and numerous varieties are dis- 

 fcinguished. In order satisfactorily- to accomplish this 

 object, all or nearly all the known varieties of the genus 

 Pisum must be considered. In this paper only the inheri- 

 tance of cotyledon color is considered. Further papers 



i Published as Brooklyn Botanic Garden Contributions, No. 10. These 

 studies on the genetics of Pisum are being carried on in collaboration with 

 the Office of Forage Crop Investigations and the Office of Horticultural and 

 Pomological Investigations, IT. S. Department of Agriculture. Based in 

 part on a paper given at the Twentieth Anniversary Celebration, New York 

 Botanical Garden, September 9, 1915. 



530 



