[58 Bird - Lore
effect of wear is shown by photomicrographs of brawn Purple Finch feathers, and the second is shown by the figures of Crosshill feathers. We have illustrated also the effect of wear on a Meadow Lark. showing how the lighterrcolored parts of feathers may disintegrate.
The growth of each feather is a chapter by itself. The histologist with microscope and cross-sections tells us how beneath the old feather. resting in a pit or follicle of the skin, certain cells group themselves and multiplv until a papilla or feather germ is formed This pushes out the
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old feather and lengthens into a pu py cylinder from the apex of which the ‘pin-feather' expands, being built by the pulp cells from the tip downward and from the edges inward as the papilla elongates. This 15 but a rude way of expressing the ven‘ elaborate process of feather~growth completed when. in the course of a few weeks. the pulp of the calamus. or quill-part of the feather. dries up. Each papilla produces a new feather at the time of a molt (and also whenever one is accidentally pulled out) and enjoys a period of test between times. The individual feathers of the natal plumage. technicallv known as "Evifflflti/PS, are ex- ceptions and are continuous in growth with the tips of the feathers of the juvenal plumage.
A melting bird is as confusing to examine as any prize puzzle, but series
