Tricotyls as Half Races and Intermediate Races. 347 
A series of this kind is, however, a purely morpho- 
logical one and neither physiological nor statistical. If 
we wish to obtain this, we must not merely pay attention 
to the forms, but also to the frequency of their occur- 
rence. In doing so the first striking fact is that all the 
aberrant forms taken together, constitute only a very 
small percentage of the total number, even smaller some- 
times than the figures already given. Therefore, if we 
construct a frequency curve the dicotyls produce a high 
peak and the curve extends from this only in one direc- 
tion and is therefore a so-called half curve. 1 
Further, amongst the aberrant forms themselves, the 
various forms occur in widely different proportions. The 
hemi-tricotyls are far rarer than the tricotyls ; the num- 
ber of all the hemi-tricotylous types together often does 
not amount to as much as that of the pure tricotyls. 
Deep clefts are somewhat less rare than shallow ones; 
and we often see specimens which at first seem to be 
purely tricotylous but which, when the peduncles of the 
cotyledons gradually elongate, turn out to be deeply cleft. 
This is particularly evident in Amarantus speciosus and 
Antirrhinum majus (Fig. 63 B), in which the closer 
juxtaposition of two of the cotyledons betrays the fact 
that they arise from a common stalk. Hemi-tetracotyls 
are always much rarer than tricotyls in sowings from 
commercial seed as well as in selected races. Neverthe- 
less some species seem to be richer in them than others. 
If we plot such a frequency distribution we obtain 
a two-peaked curve which has a small secondary apex 
over the ordinate for the tricotyls, besides the main one 
for the dicotyls. Thus I found a crop of 800 seedlings 
of Cannabis sativa of 1894 to have the following com- 
1 See above, p. 26. 
