been negative, as would ordinarily be expected. ‘Thus 
the formation of ‘Quinde’-type leaves by apparently 
healthy seedlings implies that the typical leaves of 
‘Quinde’ trees are formed independently of the virus 
(CDV) infecting them. 
One may compare the successive occurrence of differ- 
ently shaped leaves to the widely encountered phenome- 
non of juvenility, but in so doing it must be noted that 
only four of the D. candida cultivars are involved, while 
the other five are not. I have not seen any descriptions 
of juvenile leaves in the genus Datura. 
Blakeslee found a variant of D. Stramonium with a 
leaf similar but not identical to that of ‘Quinde’ (1). He 
named these ‘Quercina’ and soon established that their 
unusual leaf shape depended upon asingle recessive gene. 
Curiously, he also discovered that the juices of the plant 
would transmit the characteristic to normal JD. Stramo- 
nium, and he believed that the Quercina effect was caused 
both by a gene and by avirus. Further studies of the sup- 
posed virus have not been undertaken to my knowledge. 
Geographical centre of dwersity 
More variation in Datura candida is found in the Val- 
ley of Sibundoy than is known at any other locality. 
Such acentre of diversity in an isolated valley apparently 
inhabited by ancient agriculturists suggests the possibili- 
ty of domestication and early evolution here. However, 
that the Valley of Sibundoy is not the centre of origin 
of any tree Datura is attested by the absence of all Da- 
tura spp., and any solanaceous plants resembling them, 
in the non-cultivated flora. Were the Valley the site of 
domestication, we would expect to find some plants capa- 
ble of self-reproduction, either sexually or asexually, and 
not wholly dependent upon man for survival. Evidently 
one or more clones of D. candida were brought into the 
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