. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. REPRODUCTION, VEGETABLE (VEGETABLE OVUM). 217 of the nucleus there exists an ovoidal embryo- cells contained previously in its cavity, to its sac, which owes it origin to the coalescence of a vertical and axial series of cells. At this period it contains only granules of starch and membrane. By the continuation of this pro- cess, the sac becomes a second time filled with cellular tissue.* Two or three of the cells sub- jacent to the micropyle end of the embryo- Fig. Section of nucleus of cvide of Finns Austriaca, i
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. REPRODUCTION, VEGETABLE (VEGETABLE OVUM). 217 of the nucleus there exists an ovoidal embryo- cells contained previously in its cavity, to its sac, which owes it origin to the coalescence of a vertical and axial series of cells. At this period it contains only granules of starch and membrane. By the continuation of this pro- cess, the sac becomes a second time filled with cellular tissue.* Two or three of the cells sub- jacent to the micropyle end of the embryo- Fig. Section of nucleus of cvide of Finns Austriaca, in the centre of which is observed the young embryo- sac, 150 diam. mucus, the nucleus which it at first contained having disappeared. It corresponds, as will be seen as we proceed, to the internal mem- brane of the ripe macrospore of the Rhizocar- pese and Lycopodiaceae. The pollen grain in theConiferasgenerally itself reaches the summit of the nucleus by means of the wide micropyle. From each grain emanates a tube, which pene- trates for a short distance into the tissue of the nucleus ; not, however, until it has re- mained for some time upon its summit. In the meantime numerous free nuclei have be- come visible in the embryo-sac, which imme- diately afterwards " presents itself filled with a large number of radially elongated cells, which are arranged in a concentric ; These continue to multiply by septa in all three directions, until the beginning of winter, at which period the wall of the embryo-sac is so delicate as to be indistinguishable. During the winter months these cells undergo no further change, except that their walls are thickened by internal gelatinous deposition. lu the beginning of March of the second year, both the gelatinous material and the cell-wall disappear, the primordial sacs lying free_ in the cavity of the embryo-sac, each containing a large globular nucleus. Shortly after, the nucleus "of each cell disappears, and is re- placed
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