. Introduction to structural and systematic botany, and vegetable physiology. Botany. THE EMBRYO. 325 embryo is always near to and points towards the micropyle of the seed, viz. to what was the orifice of the ovule; and if the embryo be straight (as in Fig. 605), or merely partakes of the curvature of the seed, the cotyledons point to the opposite extremity of the seed, that is, to the chalaza. The position of the radicle as respects the hilum varies with the different kind of seed. In the orthotropous form, as in Helianthemum (Fig. 600) and Buckwheat (Fig. 606), the radicle necessarily points
. Introduction to structural and systematic botany, and vegetable physiology. Botany. THE EMBRYO. 325 embryo is always near to and points towards the micropyle of the seed, viz. to what was the orifice of the ovule; and if the embryo be straight (as in Fig. 605), or merely partakes of the curvature of the seed, the cotyledons point to the opposite extremity of the seed, that is, to the chalaza. The position of the radicle as respects the hilum varies with the different kind of seed. In the orthotropous form, as in Helianthemum (Fig. 600) and Buckwheat (Fig. 606), the radicle necessarily points directly away from the hilum. In the anatropous form, as in the seed of the Lin- den (Fig. 599) and Violet (Fig. 604, 605), the extremity of the radicle is brought to the immediate vicinity of the hilum ; and so it is, although in a different way in the campylotropous seed (Fig. 620, 621) ; while in the amphitro- pous, the radicle points away from the hilum laterally, at a right angle to the funiculus. As the nature of the ovule and seed may usually be ascertained by external inspection, so therefore the situa- tion of the embryo within, and of its parts, may often be inferred without dissection. But the dissection of seeds is not generally a difficult operation. 639. The position of the embryo as respects the albumen, when that is present, is various. Although more commonly, in the axis, it is often excentric, or even external to the albumen, as in all Grasses and cereal Grains (Fig. 622-624), in Polygonum (Fig. 1111), &c. "When external or neai'ly so, and curved circularly around the albu-. men, as in Goosefoot, Chickweed (Fig. 621), and Mirabilis (Fig. 616), it is said to be peripheric. When bent or folded in such a FIG. 620. CampylotropouB seed of the common Chickweed (Stellaria media), magniiied. FIG. 621. Section of the same, showing the embryo coiled around the outside of albumen. FIGr. 622. Vertical section of a grain of Indian Com, passing through the embryo
Size: 1553px × 1608px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorgra, bookcentury1800, bookdecade1850, booksubjectbotany
