The principles of biology . whether, goingfurther, as it often does, it gives rise to tertiary ribs, isclearly determined by the supply of materials for growth;since such higher developments are habitually most markedat points where the nutrition is greatest-; namely, next thestem. But the clearest evidence is afforded among the Algce,which, not drawing nutriment from roots, have their partsmuch less mutually dependent; and are therefore capable ofshowing more clearly, how any part may remain an append-age or may become the parent of appendages, according tocircumstances. In the annexed Fig. 1
The principles of biology . whether, goingfurther, as it often does, it gives rise to tertiary ribs, isclearly determined by the supply of materials for growth;since such higher developments are habitually most markedat points where the nutrition is greatest-; namely, next thestem. But the clearest evidence is afforded among the Algce,which, not drawing nutriment from roots, have their partsmuch less mutually dependent; and are therefore capable ofshowing more clearly, how any part may remain an append-age or may become the parent of appendages, according tocircumstances. In the annexed Fig. 130,representing a branch of Ptilota plumosa,we see how a wing grows into a wing-bear-ing branch, if its nutrition passes a certainpoint. This form, so strikingly like that ofthe feathery crystallizations of many inor-ganic substances, proves to us that, as insuch crystallizations, the simplicity or com-plexity of structure at any place, dependson the quantity of matter that has to bepolarized at that place in a given time.*. /J9 * How the element of time modifies the result, is shown hy the familiar fact thatcrystals rapidly formed are small; and that they become larger when they areformed more slowly. If the quantity of molecules contained in a solution is rela-tively great, so that the mutual polarities of the molecules crowded together inevery place throughout the solution are intense, there arises a crystalline aggre-gation around local axes ; whereas, in proportion as the local action of moleculeson one another is rendered less intense by their wider dispersion, they become i4 MOEPHOLOGICAI, DEVELOPMENT. Hence, then, we are not without an interpretation of thoseover-developments wJtiich the phsenogamic axis occasionallyundergoes. Fig. 104, represents bud in itsrudimentary state. The lateral process b, which ordinarilybecomes a foliar appendage, differs very little from theterminal process c, which is to become an axis—differsmainly in having, at this peri
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Keywords: ., bookcentury1800, bookdecade1860, booksubjectbiology, bookyear1864
