. The elements of botany for beginners and for schools. Botany. SECTION 3.] SEEDLINGS. 23 constructed upon one and the same plan, namely, that of two leaves on a caulicle or initial stem, — a plan which is obvious even when one cotyledon becomes very much smaller than the other, as in the rare instance of Abro- nia (Fig. 54, 55). In other words, the embryos so far examined are all 37. Dicotyledonous, that is, two-cotyledoned. Plants which are thus similar in the plan of the embryo agree likevnse in the general structure of 46 48 50 62. their stems, leaves, and blossoms; and thus form a class,
. The elements of botany for beginners and for schools. Botany. SECTION 3.] SEEDLINGS. 23 constructed upon one and the same plan, namely, that of two leaves on a caulicle or initial stem, — a plan which is obvious even when one cotyledon becomes very much smaller than the other, as in the rare instance of Abro- nia (Fig. 54, 55). In other words, the embryos so far examined are all 37. Dicotyledonous, that is, two-cotyledoned. Plants which are thus similar in the plan of the embryo agree likevnse in the general structure of 46 48 50 62. their stems, leaves, and blossoms; and thus form a class, named from their embryo Dicotyledones, or in English, Dicotyledonous Plants. So long a name being inconvenient, it may be shortened into Dicotyls. 38. Polycotyledonous is a name employed for the less usual case in which there are more than two cotyledons. The Pine is the most famiUar case. This occurs in all Pines, the number of cotyledons varying from three to twelve; in Fig. 56, 57 they are six. Note that they are all on the same level, that is, belong to the same node, so as to form a circle or whorl at the summit of the caulicle. When there are only three cotyledons, they divide the space equally, are one third of the circle apart. When only two they are 180° apart, that is, are opposite. 39. The case of three or more cotyledons, which is constant in Pines and in some of their relatives (but not in all of them), is occasional among Dicotyls. And the polycotyledonous is only a variation of the dicotyledonous type, — a difference in the number of leaves in the whorl; for a pair is a whorl reduced to two members. Some suppose that there are really only Fig. 46. Section of a seed of a Peony, showing a very small embryo in the albumen, near one end. 47. This embryo detached, and more magnified. Fig. 48. Section of a seed of Barberry, showing the straight embryo in the middle of the albumen. 49. Its embryo detached. Fig. 50. Section of a Potato-seed, showing the embryo coile
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Keywords: ., bookpublishernewyorkamericanboo, booksubjectbotany, bookyear1887
