the: te:af 
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sunny wall; the vine creeps up the latticed porch to find 
the sun. Plant an oak in a broad and roomy field, and its 
tall trunk will not shoot up bare of branches. Wherever 
leaves can face the sun, there the branches will grow and 
spread, and there the leaves will lie in a lacy pattern, no 
one in the shadow of the other. 
The very humblest plants contain no chlorophyll; they 
cannot absorb and prepare the air-food, but must, like 
the mistletoe which twines about the oak, fasten them¬ 
selves upon some other plant, and steal food from their 
hosts. Such plants—and there are many—are called pat- 
asites, from the Greek words para, “beside, and sitos, 
“food.” 
Why must the tree eat? We know why we need food, 
we need it to keep our bodies warm. When you are 
healthy, if you put a doctor’s thermometer in your mouth 
you will find that your bodily temperature is ninety-eight 
degrees; even on the coldest winter day, when your toes 
and fingers are numb and your nose as red as an apple, 
your body temperature will not sink below ninety-eight. 
The food we eat is the fuel which keeps our bodily fires 
hot. But a tree has no such high temperature; the tree 
lives at a low temperature, it moves very little and uses 
up no energy running about as we do. Compared with 
an animal, a tree is only half awake, and anything that 
is half asleep uses up less energy than a running, hunting 
