THE ENERGY OF THE PLANT 277 
many of the Alge and Fungi, and the antherozoids of most 
of the other Cryptogams effect this locomotion by means of 
cilia which wave to and fro vigorously in the water in 
which they find themselves. The proportionate amount of 
energy which they expend in this way is very great com- 
pared with the total amount which they possess. Other 
movements which are not dependent upon ciliary action 
are not uncommon. The amceboid movements of the 
Myxomycetes or slime fungi, the rotation and circulation 
of the sap in many cells, the other internal movements of 
protoplasm, the hitherto unexplained movements of diatoms 
and the oscillations of certain filamentous Alge, illustrate 
these. All alike are dependent upon a certain expenditure 
of energy. 
The so-called movements of the growing parts of plants 
are frequently quoted in this connection. As we shall see 
hereafter, however, these are usually changes of position 
induced by variations in the processes of growth, and may 
rather be referred to expenditure of energy in connection 
with the latter than to actual movement. The movements 
of adult organs are also effected by causes which corre- 
spond in great measure to those which modify growth, 
being generally brought about by such variations in the 
turgescence of particular cells or groups of cells as those 
upon which we shall see growth largely depends. In this 
sense they are to be associated with modifications of the 
hydrostatic tensions in the parts concerned. A certain 
amount of expenditure of energy in the cells concerned is, 
however, most probable, though it is uncertain how far 
such changes as modify the resistance of the protoplasm to 
the passage of water through it involve the application of 
energy. The establishment and maintenance of the turgid 
condition, due to the hydrostatic distension of the extensible 
cell-wall, also demands the expenditure of energy. 
We have instances of what we may call the passive 
escape of energy in the shape of heat, and to a less extent 
in the manifestation of the phenomena of so-called phos- 
