. Elementary botany. Botany. 230 MORPHOLOG V. apple (podophyllum) and through the ovules when they are quite young, we shall find that the ovule has a structure like that shown in fig. 301. At ot is a cell much larger than the surround- ing ones. This is the macrospore. The tissue surrounding it is called here the nucellus, but because it contains the macrospore it must be the macrosporangium. The two coats or integuments of the ovule are yet short and have not grown out over the end of the nucellus. This macrospore increases in size, forming first a cavity or sac in the nucellus, the embryo s
. Elementary botany. Botany. 230 MORPHOLOG V. apple (podophyllum) and through the ovules when they are quite young, we shall find that the ovule has a structure like that shown in fig. 301. At ot is a cell much larger than the surround- ing ones. This is the macrospore. The tissue surrounding it is called here the nucellus, but because it contains the macrospore it must be the macrosporangium. The two coats or integuments of the ovule are yet short and have not grown out over the end of the nucellus. This macrospore increases in size, forming first a cavity or sac in the nucellus, the embryo sac. The nucleus divides. Fig. 301 i'6- Jul. Young ovule (macrosporangium) of podophyllum, w, nucellus containing the one-celled stage of the macrospore ; , inner integument; ojnt, outer integument. several times until eight are formed, four in the micropylar end of the embryo sac and four in the opposite end. In some plants it has been found that one nucleus from each group of four moves toward the middle of the embryo sac. Here they fuse to- gether to form one nucleus, the endosperm nucleus or definitive nucleus shown in fig. 302. One of the nuclei at the micropylar end is the egg, while the t (Vo smaller ones nearer the end are the. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Atkinson, George Francis, 1854-1918. New York, H. Holt
Size: 1555px × 1606px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, bookpublisher, booksubjectbotany
