=Kinds of Stems.=--_The stem may be so short as to be scarcely distinguishable._ In such cases the crown of the plant--that part just at the surface of the ground--bears the leaves and flowers; but this crown is really a very short stem. The dandelion, Fig. 33, is an example. Such plants are often said to be =stemless=, however, in order to distinguish them from plants that have long or conspicuous stems. _These so-called stemless plants die to the ground every year._ [Illustration: FIG. 53.--STRICT SIMPLE STEM OF MULLEIN.] [Illustration: FIG. 54.--STRICT UPRIGHT STEM OF NARROW-LEAVED DOCK.] [Illustration: FIG. 55.--TRAILING STEM OF WILD MORNING GLORY (_Convolvulus arvensis_).] Stems are =erect= when they grow straight up (Figs. 53, 54). They are =trailing= when they run along on the ground, as melon, wild morning-glory (Fig. 55). They are =creeping= when they run on the ground and take root at places, as the strawberry. They are =decumbent= when they lop over to the ground. They are =ascending= when they lie mostly or in part on the ground but stand more or less upright at their ends; example, a tomato. They are =climbing= when they cling to other objects for support (Figs. 36, 56). [Illustration: FIG. 56.--A CLIMBING PLANT (a twiner).] Trees in which the main trunk or the “leader” continues to grow from its tip are said to be =excurrent= in growth. _The branches are borne along the sides of the trunk_, as in common pines (Fig. 57) and spruces. Excurrent means _running out_ or _running up_. [Illustration: FIG. 57.--EXCURRENT TRUNK. A pine.] Trees in which the main trunk does not continue are said to be =deliquescent=. _The branches arise from one common point or from each other._ The stem is lost in the branches. The apple tree, plum (Fig. 58), maple, elm, oak, China tree, are familiar examples. Deliquescent means _dissolving or melting away_. [Illustration: FIG. 58.--DELIQUESCENT TRUNK OF PLUM TREE.] =Each kind of plant has its own peculiar habit or direction of growth=; spruces always grow to a single stem or trunk, pear trees are always deliquescent, morning-glories are always trailing or climbing, strawberries are always creeping. We do not know why each plant has its own habit, but the habit is in some way _associated with the plant’s genealogy or with the way in which it has been obliged to live_. The stem may be =simple= or =branched=. A simple stem usually grows from the terminal bud, and side branches either do not start, or, if they start, they soon perish. Mulleins (Fig. 53) are usually simple. So are palms. _Branched stems may be of very different habit and shape._ Some stem systems are narrow and erect; these are said to be _strict_ (Fig. 54). Others are _diffuse_, _open_, _branchy_, _twiggy_.