36 THE AMERICAN BOTANIST 
are. In some cases we say, and rightly, they are hereditary ; but 
this explains nothing, it only implies that there was a time when 
the structure was different from what it has since become. What 
brought about the change, and why has it become fixed and 
hereditary^ ? 
Again, we say glibly — but, no doubt, with some truth — that 
these double flowers are the result of some differences in the con- 
ditions under which plants grow — to a difference in the ''environ- 
ment," as it is the fashion now to say. These changes bring 
about a corresponding alteration in the nutrition of the plant, 
and so on. All this is true enough, but it is not sufficient for 
practical purposes. We still want to know how and why. The 
difficulty of finding out is increased by the fact that we constantly 
find one plant out of many producing double flowers, or it may 
even be one flower out of several on the same branch, that is 
doubled, while all the others are normal, and yet the ''environ- 
ment" is, for aught we can see, unchanged. 
Of late years the production of double flowers has been at- 
tributed to the action of mites or other insects, to fungi, and quite 
recently to the influence of nematode worms in the roots. It can- 
not be denied that such causes may be operative. All that we can 
say is, that although we are pretty familiar with double flowers in 
a wild and in a cultivated state, as also with the effects of injury 
from insects and fungi of various kinds, yet we have never seen 
any such morphological changes as are exhibited in "double" 
flowers as a result of parasitic injury. What we do find in such 
case are pathological deformities in which regularity of conforma- 
tion is abolished, and more or less shapeless masses ensue, or, as 
in the case of galls, we find a regular adaptation to the require- 
ments of the insect.— Gardener s Chronicle. 
SURVIVAL OF DESERT AND ALPINE PLANTS. 
Many seemingly inhospitable regions possess a comparatively 
rich flora and the wonder is, how the various species manage to 
.survive in such places. A hint in the matter is given by Elias 
Nelson in the Plant World, who, writing of the Rocky Mountain 
