. Contorni di botanica per la High School di laboratorio e aula (basato su Grey's lezioni di botanica) preparata su richiesta del Dipartimento di Botanica dell'Università di Harvard. La botanica; Botanica. Lo stelo. 41. Viticci ol il pas- siini fiore. Viticcio è noto per la sua posizione. Un vitigno dalla axil di una foglia, come quella del fiore della passione (Fig. 41), è naturalmente un gambo, ossia una In anch'. 80. Nelle giovani- stadio, wlien ancora ex- tendeva, viticci sono dotati witli motion e con i sensibili- ness per contatto. I loro movimenti sono simili a quelli di twining steli, - tliey de- scribe cerchi o el- lipses onu

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. Outlines of botany for the high school laboratory and classroom (based on Gray's Lessons in botany) Prepared at the request of the Botanical Dept. of Harvard University. Botany; Botany. THE STEM. 41. Tendrils ol the Pas- siini Flower. tendril is known by its position. A tendril from the axil of a leaf, like that of the Passion Flower (Fig. 41), is, of course, a stem, i.e. a In'anch. 80. In the young- stage, wlien still ex- tended, tendrils are endowed witli motion and with sensitive- ness to contact. Their movements are like those of twining stems, — tliey de- scribe circles or el- lipses until brought against some object. When, by the curving of the ti[), a hold has been secured upon this object, the tendril coils in a double spiral. The coil or spiral itself is of importance in all such cases, for its elasticity prevents a sudden stress caused, for example, by a bla.st of wind, from snapping the tendril off, as might be the result were the tendril straight and already tiglitly drawn at the moment of onslaught. " I have more tliaii once gone on purpose, during a gale, to watch a Bryony growing in an exposed hedge, witli its tendrils attached to the surrounding bushes; and as the tliick and thin branches were tossed to and fro by the wind, the tendrils, had they not been excessively elastic, would instanth' have been torn olf and the plant thrown pro.s- trate. But as it was, the Bryony safely rode out the gale, like a ship with two ancliors down, and with a long range of cable ahead to serve as a spring as she surges to the storm." — D.rwix. 81. The tendrils of the Passion Flower are wonderfully sensitive to sliglit pressure. In Darwin's experiments, "A bit of platinum wire, .'(, of a grain in weight, gently placed on the concave point, caused a tendril to become hooked, as did a loop of soft, thin cotton thread J^ of a grain. The point of a tendril of Pas.tiflora gracilis began to move distinctly in twenty five seconds after a touch, and in ma

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• bookcentury1900
• bookdecade1900
• booksubjectbotany
• bookyear1901