352 Tricotyloiis Races. 



some higher ones which not rarely attain a value of 10% 

 to 20 % and in rare cases even of 30% to 40 %. 



Whenever the cultivation in the garden gives no 

 ground for the assumption of special influences the differ- 

 ence between the values derived from the original com- 

 mercial samples of seed and the self -harvested seed of 

 the first year must be attributed almost exclusively to 

 the fact that the commercial seed was a mixture whilst 

 the self -harvested crops matured in isolation. But since 

 mixtures of this kind have been the rule during the gen- 

 erations which preceded the purchase of the commercial, 

 horticultural or agricultural, seeds, it is evident that 

 those species which contain a number of rich seed-parents 

 every year, will give a higher percentage of tricotyls in 

 the mixture than others. Thus the percentage compo- 

 sition of commercial seed gives some idea of what may 

 be expected from it by subsequent culture. 



In the following sections (§§2-8) I shall describe 

 my experiments on these two groups in detail. Here, 

 however, I will give the main result. It is this: 



By far the largest number of spacies contain only 

 a half race in respect to tricotyly, but some few also con- 

 tain, besides this, the intermediate race. If the latter is 

 present in commercial seed or in seed obtained by ex- 

 change, it can be easily and speedily isolated; but if it 

 is not present years of selection cannot bring it out. The 

 half race and the intermediate race are, here as else- 

 where, perfectly distinct things, which do not merge into 

 one another, or if they do, they do so only by chance. 



Sometimes, but on the whole very seldom, an indi- 

 cation of the likelihood of obtaining tricotylous inter- 

 mediate races may be afforded in nurseries and in agri- 

 culture. This consists in species with a decussate ar- 



