280 Glandular Hairs of Plants. [ May, 
For our present purpose enough of these hairs and glands 
have been described and illustrated. A large majority of plants 
j possesses something 
of this nature in a 
greater or less de- 
= ==~ gree. When fresh, 
and especially when 
not exposed to di- 
rect sunlight or air 
which is too dry, 
these glands are cov- 
ered with a spherical 
glistening drop which is often several times the diameter of the 
gland. 
The uses of these hairs and glands we probably now under- 
stand to some extent, but in other cases we can only guess their 
office. The slender-pointed hairs may serve to some extent to 
ward off insects. These and the scale-like hairs may prevent the 
delicate surface from being scorched by the sun. This is not 
very probable, because most of the hairs on leaves are on the 
under side away from the direct rays of the sun. In the case of 
the common mullein, the thick branching hairs probably make the 
plant offensive to cattle and other animals. In a similar way 
other plants are protected from animals. 
When packed within the bud scales during winter, the young 
leaves and flowers of many of our trees and shrubs are well pro- 
tected by these soft hairs which envelope the tender parts like a 
mass of cotton or wool. After expansion of the buds these hairs 
generally drop off. 
When the hairs or spines are stout and point backward, as 1n 
Galium and Leersia, they serve well to hold up the weak plant as 
it rises among stouter objects. 
Fruit with hooked hairs is likely to be scattered by holding 
fast to animals. The bloom ona cabbage leaf or plum, and the 
thick hairs on plants prevent them from becoming wet on the 
surface. The shield and star-shaped scales on Shepherdia and 
Deutzia, and others, may serve the same purposes as hairs. These 
delicate objects must protect the plant from injury on account of 
sudden changes of the weather. The advantage of the sting of 
Fic. 43.—Glands on petiole | of Snowball. 
the nettle to the plant is obviously a means of self-protection. 
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