SCIENCE IN THE PLANT WORLD 
this fact in the cultivation of certain varieties of 
Hortensia. ? 
The chemical activities of plants are of in- 
calculable value to man. They change air, 
water and mineral salts into forms easily assim- 
ilable by the human system. Eliminate all the 
vegetable life from this planet, and the animals, 
including man, would perish in a few months. 
Man has also learned to make abundant use of 
plant substances for innumerable purposes. 
Potash is an example of how the plants come 
to our aid in furnishing us a valuable chem- 
ical. It is extracted from wood, Seaweed and 
Banana stalks. ‘These plants have discovered 
a way of getting it out of its well-nigh insoluble 
earth combinations with silica. If it had not 
been for certain industrious sea plants, man 
would probably never have been aware of the 
important chemical twins, bromine and iodine, 
so important in photography. These plants 
patiently filter them out of sea water where they 
exist in microscopic quantities, and build them 
into their bodies. Beer is possible because 
germinating grains transform amylum or plant 
starch into sugar. We find ripe fruits palatable 
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