the source of a fibre, a narcotic, a medicine, an oil, and 
an edible fruit (2, 7, 18, 19, 20). 
Native apparently somewhere in central Asia, where 
it occurs as a plant of open, disturbed habitats, such as 
riverbanks, bottomlands, and hillsides, hemp has spread 
to all parts of the world where conditions are suitable for 
its growth: in fact, it is at present one of the most 
widely disseminated cultivated plants (4, 18, 29, 81). 
The effects of man’s subconscious and later conscious 
selection for desirable characteristics combined with the 
effects of natural selection under the stress of new and 
sometimes inhospitable environments have acted signifi- 
cantly in morphologically and perhaps chemically alter- 
ing the Cannabis plant. As a result, today, possibly 
some 10,000 years after the beginnings of the man-hemp 
partnership, Cannabis has become one of the most vari- 
able of cultivated plants. 
It is precisely this variability and our lack of anything 
approaching a full understanding of its nature and extent 
that have created a most difficult problem for systema- 
tists who have attempted to delimit specific and sub- 
specific boundaries in the genus. 
Unlike some domesticated plants, Cannabis is believed 
still to occur in wild populations in certain parts of Asia 
and to exhibit in these populations an appreciable amount 
of inherent natural variability (5, 29). Man took advan- 
tage of this variability as he domesticated Cannabis by 
cultivating and artificially selecting for a number of use- 
ful traits, such as elongated bast fibres, large seeds with 
high oil content and copious production of narcotic resin. 
Under the pressures of selection for these characters, 
Cannabis began to reveal characters and combinations of 
characters not found in wild or presumed wild popula- 
tions, a phenomenon that has occurred in every plant 
domesticated by man. 
[ 888 | 
