possible that many of these single recessive genes affect- 
ing taxonomically significant characters are present also 
in the tree Daturas. In Colombia, I have observed un- 
usual tree Daturas which resemble the striking effects 
produced in herbaceous species by the single recessive 
genes ‘‘equisetum’’, ‘‘tricarpel’’ and ‘‘quercina’’ (Bris- 
tol 1112, 1162, 566; GH). 
Many writers have noticed the frequency with which 
the tree Daturas are associated with human habitations, 
but the extent of this association and its implications 
have not been fully understood. I have seen no indica- 
tion in herbaria nor during 18 months of field work in 
southern Colombia and northern Ecuador that any tree 
Datura was not associated with human activity; and 
Schultes (pers. comm.), in his many years of familiarity 
with northwestern South America, has never seen a tree 
Datura that he could say was truly wild. The northern 
Andes, however, is the centre of variability and probable 
area of origin of this group. In the same region, there is 
a conspicuous absence of seedling tree Daturas, although 
Schultes once observed abundant seedlings of D. vul- 
canicola. 'The reason for the usual failure of seeds to re- 
generate colonies is obscure, but it may relate to the 
normal indehiscence of fruits; if given normal care in a 
greenhouse, seeds of D. candida and D. sanguinea pro- 
duce healthy seedlings. Throughout the northern Andes, 
it is customary for man to propagate tree Daturas by 
large cuttings. As no other mode of reproduction appears 
to be operative, and since they are nowhere encountered 
as an element of natural vegetation, it appears that the 
tree Daturas have achieved their present, highly orna- 
mental form under domestication and thus should be 
considered as cultigens. 
If we reflect upon this occurrence of highly attractive, 
medicinally and narcotically useful plants possessing 
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