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vii
INTRODUCTION.

§ 4. The Stem.

28. Stems are

erect, when they ascend perpendicularly from the root or stock ; twiggy or virgate, when at the same time they are slender, stiff, and scarcely branched.

decumbent or ascending, when they spread horizontally, or nearly so, at the base, and then turn upwards and become erect.

procumbent, when they spread along the ground the whole or the greater portion of their length ; diffuse, when at the same time very much and rather loosely branched.

prostrate, when they lie still closer to the ground.

creeping, when they emit roots at their nodes. This term is also frequently applied to any rhizomes or roots which spread horizontally.

tufted or cæspitose, when very short, close, and many together from the same stock.

29. Weak climbing stems are said to twine, when they support themselves by winding spirally round any object ; such stems are also called voluble. When they simply climb without twining, they support themselves by their leaves, or by special clasping organs called tendrils (169), or sometimes, like the Ivy, by small root-like excrescences.

30. Suckers are young plants formed at the end of creeping, underground rootstocks. Scions, runners, and stolons, or stoles, are names given to young plants formed at the end or at the nodes (31) of branches or stocks creeping wholly or partially above-ground, or sometimes to the creeping stocks themselves.

31. A node is a point of the stem or its branches at which one or more leaves, branches, or leaf-buds (16) are given off. An internode is the portion of the stem comprised between two nodes.

32. Branches or leaves are

opposite, when two proceed from the same node on opposite sides of the stem.

whorled or verticillate (in a whorl or verticil), when several proceed from the same node, arranged regularly round the stem ; geminate, ternate, fascicled, or fasciculate when two, three, or more proceed from the same node on the same side of the stem. A tuft of fasciculate leaves is usually in fact an axillary leafy branch, so short that the leaves appear to proceed all from the same point.

alternate, when one only proceeds from each node, one on one side and the next above or below on the opposite side of the stem.

decussate, when opposite, but each pair placed at right-angles to the next pair above or below it ; distichous, when regularly arranged one above another in two opposite rows, one on each side of the stem; tristichous, when in three rows, etc. (92).

scattered, when irregularly arranged round the stem ; frequently, however, botanists apply the term alternate to all branches or leaves that are neither opposite nor whorled.

secund, when all start from or are turned to one side of the stem.

33. Branches are dichotomous, when several times forked, the two branches of each fork being nearly equal ; trichotomous, when there are three nearly equal branches at each division instead of two ; but when the middle branch is evidently the principal one, the stem is usually said to have two opposite branches ; umbellate, when divided in the same manner into several nearly equal branches proceeding from the same point. If however the central branch is larger than the two or more lateral ones, the stem is said to have opposite or whorled branches, as the case may be.

34. A culm is a name sometimes given to the stem of Grasses, Sedges, and some other Monocotyledonous plants.


§ 5. The Leaves.

35. The ordinary or perfect Leaf consists of a flat blade or lamina, usually green, and more or less horizontal, attached to the stem by a stalk called a footstalk or petiole. When the form or dimensions of a leaf are spoken of, it is generally the blade that is meant, without the petiole or stalk.

36. The end by which a leaf, a part of the flower, a seed, or any other organ, is attached to the stem or other organ, is called its base, the opposite end is its apex or summit, excepting sometimes in the case of anther-cells (115).