Tricotyls as Half Races and Intermediate Races. 347 



A series of this kind is, however, a purely iiKjrpho- 

 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. ^ 



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 wdiich 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 spcciosiis and 

 Antirrhinuin 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 w^ell 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 T found a crop of 800 seedlings 

 of Cannabis sativa of 1894 to have the following com- 



' See above, p. 26. 



