352 Tricotylous Races. 
some higher ones which not rarely attain a value of 10% 
to 20 % and in rare cases even of 30% to 40 %. 
\Yhenever 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 species 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- 
