206 



TiTK lorRNAI. OF ITkricditv 



raising some of the male i^lants in i)lots 

 by themselves. If male plants were 

 found to live longer alone than with 

 the female plants, it might be inferred 

 that they are starved or strangled by the 

 female plants, just as the dwarf male 

 s])idcrs are often killed and eaten by 

 their huge and hungry mates. In both 

 cases the death of the males contrib- 

 utes incidentally to the welfare of the 

 progeny, whereas their continued exist- 

 ence would not. 



OTHER VARIETIES LESS UNEQUAL 



In the ordinary varieties of hemp 

 grown for fibre or drug purposes there 

 is no such striking inequality of the 

 sexes. Though the male plants die 

 somewhat in advance of the females, 

 they attain nearly the same stature and 

 live through most of the season. The 

 variety that shows this extreme inequal- 

 ity of the sexes is recognized by L. H. 

 Dewey as the so-called Russian or 

 Manchurian hemp, which is extensively 

 grown in Europe and Asia, not for the 

 fibre, but for seed. The oil extracted 

 from the seed is used for food and also 

 has rapid-drying qualities that render 

 it of interest to manufacturers of paint 

 and varnish. The plant has not been 

 grown on a commercial scale in the 

 United States, but attention is now being 

 given to this possibility. The seed crop 

 is much larger than with the varieties 

 grown for fibre, for which the earlier 

 mortality of the males may be partly 

 responsible. Indeed, if the sexes had 

 an equal develojjment it would be hard 

 to believe that a dioecious plant could 

 compete with a bisexual species in 

 seed production. This may be a reason 

 why there are relatively few dioecious 

 plants among annuals. 



With ]iercnnial ].4ants there could 

 be no corresponding ad\antage in having 

 the males short-lived. The existence of 

 perennials is not so acutely dependent 

 upon the production of seed every year 

 as upon the ability to gain and hold 

 ground against the competition of 

 other species. In this struggle, large, 

 long-lived male plants doubtless have 

 advantages that more than counter- 

 balance the factor of com]3ctition be- 

 tween the sexes. But even with peren- 

 nials the general tendency of selection 

 is probably in favor of the bisexual 

 types and against the separation of the 

 sexes in different individuals. 



SHORTENING OF INTERNODES. 



Another pecuHarity of the oil-seed 

 hemp is that the lateral fruit-bearing 

 branches have extremely short inter- 

 nodes, analogous to those of the so- 

 called cluster varieties of cotton. The 

 shortening of the fruiting branches may 

 also be connected with the earliness 

 and productiveness of th2 crop, from 

 which high \4elds of seed are obtained. 

 This form of hemp, according to Mr. 

 Dewey, is probably the same as that 

 described by Pallas as Cannabis erratica, 

 though it is not usually considered as a 

 S]3ccies distinct from the ordinar}' 

 Cannabis sativa. It has probably been 

 cultivated in China since a very remote 

 period. References to the sexual diver- 

 sification of the hemp i)lant in Chinese 

 literature are dated as far l)ack as 

 2 700 B. C . 



NOTE. — The Editor luH called my attention 

 to a paper that is to he published in the same 

 issue of the Journal, in which a theory of sex- 

 determination appears to have been based 

 larjrely on experiments with hemp. The in- 

 ecjuality of tne sexes naturally suggests the 

 question whether the results ascribed to sex 

 determinaticm might not be due to other 

 causes, such as unequal susceptibility of the 

 seedlings to adverse envirt)nmental conditions. 



Lectures Are In Demand 



Announcement in a recent issue of the Journal of Heredity that a lecturer was 

 now available for talks on eugenics, has led to a gratifying demand for the services 

 of A. Edward Hamilton, of the Eugenics Record Office, Cold Spring Harbor, 

 Long Island, New York. He can be secured by clubs, colleges and other organiza- 

 tions which wish to give serious attention to eugenics; his services are made avail- 

 al)le through the liberality of Mrs. Iltintington Wilson, of tliis association. 



