. A manual of botany. Botany. 264 MANUAL OF BOTANY Fig. 577. body commonly called the embryo. We may have thus thi-ee distinct generations represented in the seed. 1. The megaspore and the remains of the original megasporangium, or the nucellus of the ovule with its integuments. The latter are frequently the only part of the sporangium remaining, the nucellus itself having disappeared. 2. The gametophyte, consisting of a mass of tissue called the endosperm, developed inside the spore or embryo-sac. This again is frequently only represented very slightly, or it may be altogether absent, having
. A manual of botany. Botany. 264 MANUAL OF BOTANY Fig. 577. body commonly called the embryo. We may have thus thi-ee distinct generations represented in the seed. 1. The megaspore and the remains of the original megasporangium, or the nucellus of the ovule with its integuments. The latter are frequently the only part of the sporangium remaining, the nucellus itself having disappeared. 2. The gametophyte, consisting of a mass of tissue called the endosperm, developed inside the spore or embryo-sac. This again is frequently only represented very slightly, or it may be altogether absent, having been absorbed by the embryo. 3. The new sporophyte, or embryo, which may be small and embedded in the endosperm, or maybe large, filling the embryo- sac, having absorbed the endosperm during its development. If the nucellus also has been absorbed during the growth of the embryo-sac, the seed may present to view only the em- bryo enveloped in the modified original integuments of the megasporangium or ovule. Like the ovule, the seed is either at- tached to the placenta directly, in which case it is described as sessile; or by means of a stalk, called the funiculus or funicle {figs. 512, /, and 577, /), when it is said to be stalked; its point of attachment is termed the hilum. The position of this hihim may be commonly seen on seeds which have separated from the ftuiioulus or placenta, by the presence of a scar, or by a. difference of colour to the surrounding integument. The hilum varies much in size, being in some cases very minute, but in others extending for some distance over the surface of the outer coat of the seed, as in the Horsechestnut and Calabar Bean. The hilum, as in the ovule, indicates the base of the seed. The chalaza is well seen in the Orange, and commonly in all anatro- pous seeds, in which case also the raphe may be generally noticed forming a projection on the face of the seed. The micropyle also, although smaller and less distinct than in the ovule, owing t
Size: 1619px × 1544px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, bookpublisher, booksubjectbotany
