THE PLANT AND ITS FOOD 21 
of sunlight, which enables it to construct com- 
plex carbon compounds when supplied with the 
raw materials, carbon dioxide and water. In 
other words, the chloroplast is a mechanism 
which is able to build up carbon compounds 
which are poorer in oxygen than are the raw 
materials upon which it works, and thus the 
kinetic energy supplied by the sunlight be- 
comes converted into the potential energy re- 
presented by the chemical products which are 
formed as the result of chloroplastid activity. 
This energy (which was derived from the sun), 
can again be released by oxidation, that is 
by more or less rapidly burning those products. 
It may then be utilised to heat a furnace, to 
drive a steam engine, or to maintain the bodily 
processes of a man. 
This property of the chloroplast is of funda- 
mental importance, not only for the plant, 
but for animals as well, for every animal is 
directly or indirectly nourished by vegetable 
products, which form the starting-point of the 
food-supply of the world. In the absence of 
chlorophyll there would be none of the higher 
plants as we know them, nor would there, in 
all probability, be any of the higher animals 
at all. In this sense we are indeed all children 
may be termed a syncytium. It must be borne in mind 
that the membrane is not an essential feature of cells, 
although in plants, as stated in the text, it is of very general 
occurrence. The cell contains other bodies, ¢. g. chloro- 
plasts, starch, oils, etc., but these are non-essential, and 
are often absent. 
