Book Description

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. Excerpt: ... having for nutriment the carbonic acid of the air and certain mineral components of the soil, show us modes of multiplication adapted to the fullest utilization of these substances. A herb, with but little power of forming the woody-fibre requisite to make a stem that can support wide-spreading branches, after producing a few sexless axes, produces sexual ones; and maintains its race better by the consequent early dispersion of seeds, than by a further production of sexless axes. But a tree, able to lift its successive generations of sexless axes high into the air, where each axis gets carbonic acid and light almost as freely as if it grew by itself, may with advantage go on budding-out sexless axes year after year; since it thereby increases its subsequent power of budding-out sexual axes. Meanwhile, it may advantageously transform into seed-bearers, those axes which, in consequence of their less direct access to materials absorbed by the roots, are failing in their nutrition; for in doing this, it is throwing-off from a point at which sustenance is deficient, a migrating group of germs that may find sustenance elsewhere. The heterogenesis displayed by animals of the Cajlenterate type, has evidently a like utility. A polype, feeding on minute annelids and crustaceans, which, flitting through the water, come in contact with its tentacles; and limited to that quantity of prey which chance brings within its grasp; buds out young polypes which, either as a colony or as dispersed individuals, spread their tentacles through a larger space of water than the parent alone can; and by producing them, the parent better insures the continuance of its species, than it would do if it went on slowly growing until its nutrition was nearly balanced by its waste, and...