SUN RAYS—ABBOT 165 
plasmic living cells in plants and animals have much in common. 
A plant, like an animal, is to be looked upon as a colony of cells. 
Just as in a society of bees, or of ants, some individuals are told off 
and become modified in structure to perform certain duties neces- 
sary to the life of the society as a whole, so in plants and in animals 
the protoplasmic cells are, as physiologists say, differentiated, some ~ 
for one function, some for another. By what physical agencies this 
is done is the mystery of hfe. ‘Thus, we have in the plant the root 
with a variety of cells, some for imbibing ground water, others for 
storing food during’ wintry cold, still others forming a protecting 
covering. Again in the stem are some adapted for mechanical resist- 
ance to pressures like those of winds, others promoting the passage 
of foodstutis, and still others protecting the interior from exposure. 
In the leaves there are the variety of special cells, adapted for the 
several different functions involved in nature’s solar chemistry. 
Finally, in the flowers and ripening fruits are other varieties of 
cells set apart for the many functions associated with reproduction. 
All of these modifications of the primordial cell work together in 
admirable harmony to promote hfe and growth of the cell colony 
which we call a plant. One may be apt to think of it as very inferior 
to the cell colony which we call the animal. Tor does it not lack 
a nervous system for communication, and also the capacity for 
motion? But the latest researches seem to show that the plant is 
not so deficient in these respects as might be supposed. What, for 
instance, causes a bending of the stem toward the light, and the 
development of rudimentary buds into growing shoots when the 
terminal bud is lost, if there be no communication of useful impulses 
through the body of a plant? What leads to the great storage of 
food in the root system, to prepare for the dormant period of winter, 
and for the uprush of the sap in spring, to cause the leaves and buds 
to burst forth? These are but a few of the great mysteries which, 
the closer they are studied, the higher they tend to raise our admira- 
tion. Finally, the plant kingdom has the great superiority over 
the animal that, like the farmer among men, it furnishes by its 
unique employment of solar radiation, not only the means to feed 
its own living cells, but all those of the animal world besides. 
Already, therefore, we have discovered in the plant two indis- 
pensable activities of the sun. The first is the mysterious combining 
influence of certain solar rays, which, acting in green leaves, build 
up the most complex life chemicals from such simple materials as 
carbonic acid gas of the air and weakly impregnated water from 
the ground. This is an action as yet inimitable in the laboratory. 
We have yet to learn its intricacy and causation. The second indis- 
pensable action of solar energy is to evaporate from the leaves and 
twigs enormous quantities of water. Thus are left behind, in suit- 
