. The elements of botany for beginners and for schools. Botany. SECTION 10.] PISTILS. 107 the midrib of the leaf, — not a seam therefore; but at maturity many fruits, sucli as pea-pods, opeu by this dorsal as well as by the ventral line. Placenta, a name given to the surface, whatever it be, which bears the ovules and seeds. The name may be needless vrheii the ovules grow directly on the ventral suture, or from its top or bottom ; but when there are many ovules there is usually some expansion of an ovule-bearing or seed-bearmg surface; as is seen in our Mandrake or Podophyllum, Fig. 326. 309.
. The elements of botany for beginners and for schools. Botany. SECTION 10.] PISTILS. 107 the midrib of the leaf, — not a seam therefore; but at maturity many fruits, sucli as pea-pods, opeu by this dorsal as well as by the ventral line. Placenta, a name given to the surface, whatever it be, which bears the ovules and seeds. The name may be needless vrheii the ovules grow directly on the ventral suture, or from its top or bottom ; but when there are many ovules there is usually some expansion of an ovule-bearing or seed-bearmg surface; as is seen in our Mandrake or Podophyllum, Fig. 326. 309. A Compound Pistil is a combination of two, three, or a greater number of pistil-leaves or carpels in a circle, united into one body, at least. 326 327 328 329 330 by their ovaries. The annexed figures should make it clear. A series of Saxifrages might be selected the gynoecium of which would show every gradation between two simple pistils, or separate carpels, and their com- plete coalescence into one compound and two-celled ovary. Even when the constituent styles and stigmas are completely coalesceut into one, the nature of the combination is usually revealed by some external lines or grooves, or (as in Fig. 328-330) by the internal partitions, or the number of the placenta^. The simplest case of compound pistil is that 310. With two or more Cells and Axile Placentae, namely, witli as many cells as there are carpels, that have united to compose the organ. Fig. 326. Simple pistil of Podophyllum, cut across, showing ovules borne on placenta. Fig. 327. Pistil of a Saxifrage, of two simple carpels or pistil-leaves, united at the base only, cut across botli above and below. Fig. 328. Compound 3-carpellary justil of common St. John's-wort, cut across: the three styles separate. Fig. 329. The same of shrubliy St. John's-wort ; the three styles as well as ovaries here united into one. Fig. 330. Compound 3-carpellary pistil of Tradescantia or Spiderwoi t; the three stigmas as well as
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectbotany, bookyear1887
