1912.] PUBLIC DOCUMENT — No. 31. 101 



siimably the number of nodes may be in some degree inherited, 

 and inasmuch as a longer vine, and presumably more nodes, 

 gives more opportunities for pod setting, productiveness may 

 be thus indirectly passed over from one generation to another ; 

 but we see no indication in this work, or any other with which 

 we are familiar, that the ability to produce pods is an inherit- 

 able character. 



It follows from this that in careful work in selecting for pro- 

 ductiveness in peas it will probably be more effective to follow 

 the indirect method of selecting the long vines rather than to 

 select directly the more elusive and variable character of pods 

 per vine. 



The difficulties in the way of studying heredity in plants lie 

 largely in differentiating the inherited variations from the en- 

 vironmental ; they may be reduced to a minimum by securing 

 as uniform conditions as possible and growing large numbers 

 of individuals. In such ways we may hope to learn the laws of 

 breeding and reduce its practice to a science. 



