BOTANICAL GAZETTE 
APRIL, 1895. 
Present problems in the anatomy, morphology, and biology 
of the Cactacex. 
W. F. GANONG. 
In this paper I purpose to discuss briefly the subject out- 
lined by the above title, pointing out in particular those ques- 
tions which can be settled only by study in the field, as well 
as those which require specially-collected field-material for 
their solution in the laboratory. The subject can be the more 
clearly understood and its importance the better judged if I 
give first a brief description of the anatomical, morphological, 
and biological characteristics of the family, and then add a 
short account of progress to our present state of knowledge. 
The Cactacez form asharply-defined, although phylogenet- 
ically very new, practically entirely American order, includ- 
Ing some I,000 usually badly-defined species grouped in some 
twenty worse-defined genera. Taken asa whole they exhibit 
a more extreme deviation from the normal in habits, and 
therefore in structure, than is to be found in any other large 
family of flowering plants; they offer in consequence many 
inviting problems, and as well an unusually favorable oppor- 
tunity to test some of the great principles which are con- 
cerned with the nature of adaptation and the dynamics of 
development. 
or the most part the Cactacez are dwellers in the desert 
and therefore economizers of water. To store water and to 
Protect it from evaporating under the too-great power of the 
sun, requires a condensed form and this characteristic domi- 
nates throughout the order, showing its traces even in those 
Species which have abandoned the desert habit. Containing 
often the only water-supply upon the desert, they are partic- 
ularly liable to destruction by thirsting animals, and protec- 
tion against them explains the presence of the nearly univer- 
Sal spines, the second marked characteristic of the order. 
10—Vol. XX—No. 4. 
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