. Elementary botany. Botany. GYMNOSPERMS: WHITE PINE. 209 end of the ovule. This depression is thus known as the pollen chamber. 420. Now the open scales on the young female cone close up again, so tightly that water from rains is excluded. What is also very curious, the cones, which up to this time have been standing erect, so that the open scale could catch the pollen, now turn so that they hang downward. This more certainly excludes the rains, since the overlapping of the scales forms a shingled surface. Quantities of resin aTre also formed in the scales, which exudes and makes the cone pra
. Elementary botany. Botany. GYMNOSPERMS: WHITE PINE. 209 end of the ovule. This depression is thus known as the pollen chamber. 420. Now the open scales on the young female cone close up again, so tightly that water from rains is excluded. What is also very curious, the cones, which up to this time have been standing erect, so that the open scale could catch the pollen, now turn so that they hang downward. This more certainly excludes the rains, since the overlapping of the scales forms a shingled surface. Quantities of resin aTre also formed in the scales, which exudes and makes the cone practically impervious to water. 421. The female cone now slowly grows during the summer and autumn, increasing but little in size during this time. During the winter it rests, that is, ceases to grow. With the coming of spring, growth commences again and at an accelerated rate. The increase in size is more rapid. The cone reaches maturity in September. We thus see that nearly eighteen months elapse from the beginning of the female flower to the maturity of the cone, and about fifteen months from the time that pollination takes Fig. 268, Macrosporanglum of pine int, integument; n, nu- cellus; m, macrospore. (After Hoffmeister.) (ovule). 422. Female pr othallium of the pine. —To study this we must make careful longitudinal sections through the ovule (better made with the aid of a micro- tome). Such a section is shown in fig. 269. The outer layer of tissue, which at the upper end (point where the scale is attached to the axis of the cone) stands free, is the ovular coat, or integument. Within this integument, near the upper end, there is a cone-shaped mass of tissue, which farther down continues along next the integument in a thinner strip. This mass of tissue is the nucellus, or the inacrosporangium proper. The elliptical mass of tissue within this, shown in fig. 271 is the female prothallium, or what is usually here called the endosperm. The conical portion of the nucell
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