Leaf Variation among Cannabis Species from a Controlled Garden

The genus Cannabis has had a long association with man and contains considerable variation in growth form, achene size, and chemical content. The variation has taxonomically been variously interpreted. Some maintain the genus is polytypic with at least three species (Emboden, 1974; Schultes et al., 1974). Others (Small and Cronquist, 1976) believe that it is properly viewed as monotypic: i.e. limited to C. sativa L. They do, however, recognize several infraspecific varieties. Historical aspects and rationale for the different treatments are amply covered in these papers. My work on wood anatomy (Anderson, 1974) supported the polytypic generic concept. A controlled garden (2.6 acres) is maintained at the University of Mississippi by the School of Pharmacy for the National Institute on Drug Abuse where collections from throughout the world are propagated. In 1976, 1 visited the facility several times to obtain additional vouchered wood samples from plants grown in a uniform garden. While gathering the Cannabis samples, I became aware of differences in leaf morphology. Variation in garden-grown plants has already been noted by Quimby et al. (1973), but they did not quantify their data. This report analyzes leaf form in Cannabis and compares the variation in relation to the alternative taxonomie treatments.