First lessons in botany and vegetable physiology by Gray Asa 1810-1888

Author:Gray, Asa, 1810-1888
Language: eng
Format: epub
Tags: Botany
Publisher: New York, Ivison and Phinney; Chicago, S. C. Griggs
Published: 1859-03-25T05:00:00+00:00

If such an ovule were to grow on one side more than on the other, and double up, or have its top pushed round as it enlarges, it would become a

Campyhtropous or curved ovule, as in Cress and Chickweed (Fig. 271). Here the base remains as in the straight kind, but its apex with the orifice is brought round close to it. — Much the most common form of all is the

Anatropous or inverted ovule. This is shown in Fig. 267, and 273 ; also a much enlarged section lengthwise, or diagram, in Fig. 275. To understand it, we have only to suppose the first sort (Fig. 270) to be inverted on its stalk, or rather to have its stalk bent round, applied to one side of the ovule lengthwise,^ and to grow fast to the coat down to near the orifice (/); the hilum, therefore, where the seed-stalk is to break away (k), is close to the orifice; but the chalaza (c) is here at the top of the ovule; between it and the hilpm runs a ridge or cord, called the Rhaphe (r), which is simply that part of the stalk which, as the ovule grew and turned over, adhered to its surface. — Lastly, the

Amphiiropouz or Jialf-anairopous ovule (Fig. 272) differs from the last only in having a shorter rhaphe,* ending about half-way between the chalaza and the orifice. So the hilum or attachment is not far from the middle of one side, while the chalaza is at one end and the orifice at the other.

326. The internal structure of the ovule is sufficiently displayed in the subjoined diagrams, representing a longitudinal slice of two

FIG. 270. Orthotropoup ovule of Buckwheat: c, hilum and chalaza; /, orifice.

FIG. 271. Campylotropous ovule of a Chickweed : c, hilum and chalaza j /, orifice.

FIG. 272. Amphitropous ovule of Mallow: /, orifice; A, hilum ; r, rhaphe; c, chalaza.

FIG. 273. Anatropous ovule of a Violet; the parts lettered as in the last.

THE BECEPTACLB.

[lesson 19.

ovules; Fig. 274, an orthotropous, Fig. 275, an anatropous ovule. The letters correspond in the two; c, the chalaza; f^ the orifice; r, rhaphe (of which there is of course none in Fig. 274); |?, the outer coat, called prtmine ; «, inner coat, called secundine ; n, nucleus or kernel.

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