XiTt 
FRANKINCENSE AND MYRRH 
HEN we come in the sunshine upon a patch 
of mown grass with a good proportion of 
Sweet Vernal, we experience, with all normally 
constituted mankind, a great sensory satisfaction. 
The fragrance is delicate, complex, and restful; for 
the moment all is right with the world. But why 
it should be so, it is difficult to tell. The odor- 
iferous substances in plants are usually ethereal 
oils and resins, by-products or end-products of 
certain vital chemical processes. Little is known 
of their physiological significance in the economy 
of the plant; most of them rank as waste-products. 
But should one of them turn out to be very attractive 
to the olfactory sense of welcome insect-visitors, 
such as bees, or very repellent to voracious enemies, 
such as snails, then it will tend to acquire survival- 
value, and, other things equal, to grow in strength. 
We have to think of all these new departures—for 
they must all have had their beginnings—as like 
tendrils probing the unknown. If they get no 
encouragement they come to little, except in so 
far as they are the necessary corollaries of indis- 
pensable antecedent processes; if they find a 
support they grow strong. Thus some of the 
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