. Class-book of botany : being outlines of the structure, physiology and classification of plants : with a flora of the United States and Canada. Botany; Botany; Botany. 52 OF THE VEINS. 250. Inter-petiolar sttpules occur in a few opposite leaved tribes, as the Ga- lium tribe. Here we find them as mere bristles in Diodia while in Galium they look like the leaves, forming whorls. Such whorls, if complete, will be appar- ently 6-leaved, consisting of two true leaves and four stipules. But the adjacent stipules are often united, and the whorl becomes 102 IDS 104 105 102, Leaf of Conios
. Class-book of botany : being outlines of the structure, physiology and classification of plants : with a flora of the United States and Canada. Botany; Botany; Botany. 52 OF THE VEINS. 250. Inter-petiolar sttpules occur in a few opposite leaved tribes, as the Ga- lium tribe. Here we find them as mere bristles in Diodia while in Galium they look like the leaves, forming whorls. Such whorls, if complete, will be appar- ently 6-leaved, consisting of two true leaves and four stipules. But the adjacent stipules are often united, and the whorl becomes 102 IDS 104 105 102, Leaf of Conioselinum, tripinnate, 'with sheathing petiole. 103, Leaf of Polygonum Penn- sylvanicnm, with its (o) ochrea. 104, Culm of grass, with joint (,;), leaf (') ligule (s). 105, Leaf of pear-tree, with slender stipules. ** 251. The Ligulu of grasses is generally regarded as a double axil- lary stipule. The leaflets of compound leaves are sometimes furnished with little stipules, called stipels. 252. Stipules are often fugacious, existing as scales in the bud, and falling when the leaves expand, or soon after, as in the Magnolia and tulip-tree. OF THE VEINS. 253. Leaves, simple and compound. A leaf is simple when its blade consists of a single piece, however cut, cleft or divided; and com- pound when it cousists of several distinct blades, supported by as many branches of a compound petiole. 254. Nature of veins. The blade of the leaf consists of, (1) the frame-wovk, and (2) the tissue commonly called the parenchyma. The frame-work is made up of the branching vessels of the foot-stalk, which are woody tubes pervading the parenchyma, and conveying nourishment to eveiy part. Collectively, these vessels are called veins, from the analogy, of their functions. 255. Venation is a term denoting the manner in which the veins are divided and distributed. The several organs of venation, differing from each other only in size and position, may be termed the midviin, veins, veiulets and veinulets.
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