ROOTS AND STEMS. 25 



A decurrent leaf is formed when the blade is prolonged 

 down the sides of the stem (Fig. 85). When the basal 

 lobes of a leaf project beyond the stem and unite, as 

 shown in Fig. 86, it is perfoliate. When opposite leaves 

 unite by their bases, as in Fig. 87, they are called connate 



FIG. 90. FIG. 91. 



leaves. When only one leaf arises from a node, and the 

 leaves grow alternately on different sides of the stem (Fig. 

 88), they are described as alternate. If there are two op- 

 posite leaves at each node, and the successive pairs are 

 placed at right angles to each other, they are said to de- 

 cussate (Fig. 89). If there are three or more leaves at a 

 node (Fig. 90), they form a whorl / and when all the leaves 

 of a branch grow close together (Fig. 91), they are said to 

 be tufted, or fascicled. 



EXERCISE XI. 

 Kinds of Stems. 



Stems that have a firm texture can sustain themselves 

 in -an upright position, but weak stems must either trail 

 along the ground or attach themselves to other plants or 

 objects for support. If they trail on the ground, they are 

 said to be prostrate (Fig. 94). If they lift themselves by 

 tendrils or other means, they are described as climbing 

 (Fig. 92) ; and if they grow upward by twisting round other 

 bodies, as shown in Fig. 93, they are said to be twining. 



The stem of an herb is named a caulis ; that of a tree, 

 a trunk ; that of grasses, a culm, and that of tree-ferns 



