70 CROSSING, 



ers gave the seed-coat a lesser tendency to stick. And it was 

 fotind that the waxy gloss, common to most peas materially 

 hindered the coherence of the seeds. Two genes were found 

 which are both indispensable for a formation of this waxy 

 gloss. Plants lacking in either or both of these two genes have 

 the seeds and all other organs devoid of wax, and the seeds in 

 such plants hang together in the ripe pods with a much greater 

 frequency than in common peas. The gene which is present in 

 most plants with hard stiff pods, but lacking from those with 

 soft, clinging, shriveling pods has a very great influence upon 

 the character. No matter what the further genotype may be, 

 plants which lack this gene, and which consequently have 

 soft pods, will hardly ever be foimd to have coherent seeds. In 

 the shrivehng of the pod the seeds are broken apart. In a sim- 

 ilar way the character is affected by the genes which affect the 

 relative size of seeds and pods, for those seeds which are not 

 in close contact when ripejiing will never hang together. And 

 lastly, the gene which roimd seeds have more than wrinkled, 

 will tend by its presence to further the cohjerence. In pods 

 which contain both wrinkled and round seeds, two adjaceht 

 rounds will hang together with more tenacity than two wrink- 

 led ones, or one round and one wrinkled. 



If anyone would want to study the coherence of seeds in the 

 pea as a separate character, and without reference to the shape 

 of the pods, the nature of the epiderm, the presence or other- 

 wise of wax and of pigment, he should be considered very lucky 

 if he could merely estimate the number of genes influencing 

 the character. He would be unable to distinguish the genes, 

 and most assuredly he would tend to the assumption that these 

 genes must be fundamentally analogus in some way. 



Lang has proposed the name "pol57mery" for cases in which 

 a nimiber of genes influence one character. The objection to the 

 use of this term, and similar ones, is obviously, that their use 

 tends to make appear exceptional what is essentially common. 

 The use of the term "polymery" for those instances, in which 

 we know several genes which influence one character, makes it 



