CHAPTER IV: THE KEY 
WHAT A KEY IS, AND WHY A NAME IS DESIRABLE 
A key in the study of botany is a guide by which a student 
may trace a specimen until he finds a name for it. Having found 
-a name, he may learn from books or from friends what is known 
of its habits of growth, of its value as a food or drug, whether 
it is harmful or harmless, whether it is to be protected or 
whether war is to be waged against it. He may learn whether 
it has figured in history or the myths, and how the poets and 
artists viewed it, and may perhaps learn to see it with their 
eyes. He may watch similar specimens as they grow, and may 
add the results of his observations to the facts already recorded 
about his specimen. 
HOW A KEY FOR FUNGI IS MADE, AND WHY IT IS DESIRABLE 
In the first place, only such plants are considered as grow 
from spores and have no leaf-green. (The spore characteristic is 
one the amateur must decide upon either by seeing the spores 
or by inferring their existence from the fact that seeds do not 
appear.) There are some thirty-five thousand species of fungi 
known to botanists, so that it would be impossible to find a 
name for a specimen if one had to read at random until the right 
description for his specimen was found; but since all of these 
plants may be put in one or another of three groups, on account 
of certain points of resemblance which they have in common, 
and since these three groups may each in turn be divided and 
subdivided, one may, by selecting groups rather than individual 
specimens, find a short path to the name desired. The three 
primary groups, called classes, are made as follows : 
The first contains many mould-like fungi which resemble 
one another in microscopic characters. 
The second contains other mould-like fungi and many con- 
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