CHEMISTRY AND PHYSICS OF PLANTS. 91 
(j) Cover the end (30 to 40 centimetres) of a cucumber-plant, bear- 
ing young flower-buds, with a tight box so as to exclude all light, 
Notice that the flowers develop perfectly as to size and color, although 
in total darkness, while the leaves are small and lacking in normal 
color. 
(k) Cover in like manner a portion of a cucumber-plant bearing 
very young fruit. Notice that the fruit develops in darkness as well 
(in size at least) as in the light. 
186. Movements of Plants —Every living plant is capable 
of moving. In some cases the movement is so small that 
it is not visible to the naked eye, while in others it is very 
evident. It is popularly supposed that animals alone have 
the power of movement, and that this power is one of the 
prominent distinctions between plants and animals. In 
fact, however, no plant is wanting in the power of move- 
ment, and there are many plants which are toneh more 
active than certain animals. 
Only an outline of this interesting subject can be given 
in this place, and the student who wishes to pursue the 
subject further should consult Mr. Darwin’s book, “The 
Power of Movement in Plants,” published in 1881. 
187. Mr. Darwin has shown by‘a great number of obser- 
vations that as soon as a seed germinates every part of the 
embryo begins moving in various directions. Thus the 
little root at once begins a sort of revolving motion, its tip 
describing more or less curved figures. This revolving or 
bending in succession towards all points of a curved figure 
so as to describe an ellipse or circle is called circumnuta- 
tion, an inconveniently long word for what, is, as we shall 
see, a very common thing in plants. 
188. By the circumnutation of a root it is enabled to 
find those places in the soil which offer the least resistance 
to its passage. Moreover, it has been shown that the tip 
