VALUE OF THE HEMP PLANT 



FOR INVESTIGATING SEX 



INHERITANCE 



The Genus Cannabis Offers a Promising Field for Studying Sex Inheritance in 



Plants 



Walter Scott Malloch 

 University of Illinois, Urhana, III. 



IN 1920 Professor E. B. Babcock 

 called the attention of the genetic 

 world to the need of corroborative 

 evidence in establishing the far reaching 

 conclusions presented by the Droso- 

 phila workers.- In discussing the 

 desiderata of ideal material for genetic 

 investigation the contrast between 

 plant and animal life was pointed out. 

 The merits and demerits of the genus 

 Crepis were enumerated as an illus- 

 tration of a favorable plant which 

 could be used as a means of substan- 

 tiating the chromosome theory of 

 heredity. Having had the pleasure 

 of observing Crepis under test both 

 cytologically and genetically for several 

 years at the University of California, 

 the writer is in full accord with the 

 statements made as to the promise and 

 value of Crepis for genetic investiga- 

 tions. 



Nevertheless, Crepis and most of our 

 plants cannot be used to substantiate 

 the manner of sex inheritance. The 

 inheritance of sex in plants has been 

 studied in Bryonia by Correns^ and in 

 Lychnis by ShuU.'' It is the purpose of 

 this article to present certain observa- 

 tions in connection with the habits of 

 Cannabis sativa (hemp) and to call 



attention to the merits of this plant as 

 one particularly adapted for the inves- 

 tigation of sex inheritance. 



Hemp is commercially valuable both 

 for its fiber and for a drug, Cannabis 

 indica or hashish, Scientific investiga- 

 tions in hemp are thus worthy of 

 support from agricultural institutions, 

 from the commercial as well as from 

 the scientific standpoint. 



The genus Cannabis consists of a 

 single species and belongs to the 

 family Moraceae.^ It is advantageous 

 in genetic investigations to choose a 

 genus having two or more species with 

 the same chromosome number. In such 

 cases one can compare the loci of the 

 genes for similar characters in the two 

 species upon the chromosome map. 

 However, Humulus (hops) is a closely 

 related taxonomic genus which may 

 afford a basis for comparison. Canna- 

 bis has 10 haploid chromosomes while 

 Humulus has 20.*^ This relationship 

 has advantages as well as drawbacks 

 but it is not prohibitive of certain 

 comparative studies. The linear order 

 of the genes in equivalent chromo- 

 somes cannot be compared but one 

 may study the effect that the doubling 

 of the chromosome number has upon 



' A contribution from the Agronomy Plant Breeding Division, University of Illinois. 



2 Babcock, E. B. Crepis, A Promising Genus for Genetic Investigation. American Naturalist 

 LIV: 270-276. 1920. 



2 Babcock and Clausen, Genetics in Relation to Agriculture. McGraw-Hill Book Company 

 Inc. 1918. 



^ Shull, G. H. Sex Limited Inheritance in Lj-c/iMW (i/o/ca. Zeit. Abst. Vererb. XII. 



* Kraemer, H. Applied and Economic Botany, p. 513. 



- Bailey, L. H. Standard Cyclopedia of Horticulture, p. 567. Macmillan and Co. New 

 York. 1914. 



« IsHiKAWA, M. A. A list of the Number of Chromosomes. Bot. Mag. Tokyo 30: 420-448. 

 1916. 



277 



