50 MORPHOLOGY OF STEMS. 



to anthotaxy or inflorescence (Chap. V.), which has its own 

 terminology. But some of its terms may be conveniently 

 employed in the description of ramification unconnected with 

 flowering. 



2. FORMS OF STEMS AND BRANCHES. 



89. On the size and duration of the stem the oldest and most 

 obvious division of plants is founded, namely, into Herbs, 

 Shrubs, and Trees. 



90. Herbs are plants in which the stem does not become 

 woody and persistent, but dies annually or after flowering, down 

 to the ground at least. The difference between annual, biennial, 

 and perennial herbs has already been pointed out in the chapter 

 on the root (50-57), and the gradations between them indicated. 

 Herbs pass into shrubs and shrubs into trees through ever}' gra- 

 dation. The following definitions are therefore only general : 



91. Undershrubs, or Sujfruticose plants, are wood}' plants of 

 humble stature, their stems rising little above the surface. If 

 less decidedly woody, they are termed Sujfrutescent. 



92. Shrubs are woody plants, with stems branched from or 

 near the ground, and less than five times the height of a man. 

 A shrub which approaches a tree in size, or imitates it in aspect, 

 is said to be Arborescent. 



93. Trees are woody plants with single trunks, which attain 

 at least four or five times the human stature. Yet the name of 

 tree is not to be denied to a woody plant having a single and 

 stout trunk of less altitude ; and those which grow in a bushy 

 manner, sending up a cluster of stems from the ground to the 

 height of thirty feet or more, may still be called shrubs. 



94. The erect position, elevation above the soil, and self-sup- 

 port, are normal conditions of the stem, but are far from universal. 

 And certain kinds of stem or branches are sufficiently peculiar 

 to have received substantive names : other equally peculiar forms 

 have no special names. There are, moreover, certain organs 

 (such as spines and tendrils) which are commonly homologous 

 (12) with stems, but not always. Two kinds of erect stems 

 have special nanies in descriptive botany. 



95. Culm is a name applied to the peculiar closed-jointed stem 

 of Grasses and Sedges, whether herbaceous, as in most Grasses, 

 or woody or arborescent, as in the Bamboo. 



96. Caudex is the name technically applied to the trunk of 

 Palms (Fig. 126), Tree-Ferns, and the like, consisting of a 

 commonly simple column, the surface beset with scales, the 



