Unlike many of man’s other cultivated plants, how- 
ever, hemp never became totally dependent on man. In 
many areas where hemp was cultivated, it readily es- 
‘aped and became naturalized as an aggressive weed. 
‘Thus released from the pressures of artificial selection 
induced by cultivation, populations of naturalized Can- 
nabis underwent extensive adaptive radiation. 
In this new role, Cannabis invaded many disturbed 
habitats, especially habitats newly created by man, be- 
coming established and spreading without man’s direct 
intervention. Like many other weeds, hemp became one 
of man’s camp followers along roadsides and in rubbish 
heaps and growing on the edges of fields (1, 2, 3, 29). 
The changes invoked by the transition from domestica- 
tion to naturalization included, at least in some cases, 
reversions to characteristics peculiar to wild hemp, as has 
been known to occur in other cultivated plants. 
We thus perceive three ‘‘phases’” of Cannabis—the 
wild, the cultivated, the weedy. ‘These ‘“‘phases”’ are not 
necessarily three discreet states of existence. The last 
two ‘‘phases’’, occurring over vast areas of the world and 
under highly varied ecological conditions, have created 
the great array of phenotypic diversity which we witness 
today in cultivated and naturalized hemp. Cannabis in 
the wild state has probably adapted well to disturbed con- 
ditions. Its wild adaptive mode pre-adapted it in many 
cases to certain cultivated conditions and often made an 
easy transition back to the weedy state or ‘‘phase’’ (4, 
19, 20, 29, 30). 
Asa result of the extraordinary plasticity and vari- 
ability evident in present-day cultivated and weedy 
Cannabis, there can be no hope of unravelling the com- 
plexities encountered in the genus through a study of cul- 
tivated types alone. No certain progress can be effected, 
until the biology of wild or presumably wild populations 
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