species of both Datura and Brugmansia in being semi- 
aquatic. 
The main character of interest is the fruit, which is 
essentially the ‘‘connecting link’. Various taxonomists 
have described the fruit as a fleshy berry ; as a fleshy, de- 
hiscent berry ; and as a smooth, irregularly opening cap- 
sule. Observations on plants grown in the Experimental 
Garden at Harvard University agree with those of 
Blakeslee’s group (1) that the fruits are smooth, fleshy 
‘capsules which dehisce by irregular, longitudinal split- 
ting of the pericarp into segments that curl back and 
break apart. It was observed also, in the cultivated plants 
at Harvard, that an abscission layer forms around the 
base of the fruit. After the initial splitting of the peri- 
‘arp, this abscission layer causes the whole fruit to fall 
from the plant (Plate N XI). The fruits of Datura cera- 
tocaula are somewhat reminiscent of the smooth-capsuled 
“quercina’’ and ‘‘inermis’” mutants of D. Stramonium; 
however, they are morphologically and anatomically un- 
related to the fruits of Brugmansia. Rather than view- 
ing Datura ceratocaula as a primitive, connecting link 
between Datura and Brugmansia, it seems more appro- 
priate to view it as a highly specialized Datura. The 
hollow stem, weak root system, and reduced vascular 
tissue are obvious specializations for its semi-aquatic 
habit. ‘The possible advantages of a fleshy fruit are not 
as apparent; however, a dry, spiny capsule would be of 
less advantage here than in a xeric environment. With 
these specializations, J. ceratocaula has exploited an eco- 
logical niche unavailable to other species of Datura 
and makes it difficult to interpret them as representing 
primitiveness, 
Due to the presence of various natural crossability 
barriers, it is rare to find Datura hybrids in the field. 
In the laboratory, however, most species can be hybri- 
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