26 THE VEGETABLE WORLD. 
herbaceous; and the stems of the leek, the cactus, and some of the 
euphorbias, are called succulent. Fig. 26 represents the stem of a 
cactus in flower. 
In a great number of plants the stem rises firm and straight 
into the air. It is then called an upright stem. There are some, 
on the contrary, which have not consistence enough to keep them- 
selves upright; they stretch along the ground, only lifting up their 
heads, so to speak; these are procumbent stems; or, being quite 
prostrate, they are fixed by adventitious roots or sunken, and are 
called creeping stems. : 
Fig. 27 represents the procumbent stem of the Veronica 
Fig. 26.—Stem and Flowers of a Cactus. 
officinalis. Others, like the ivy, hang on to neighbouring bodies by 
the aid of their suckers or adventitious roots ; or, like the bindweed, 
they entwine themselves spirally round trees. The first are called 
scandent stems, the latter volubile. 
olubile stems do not all*twine in the same manner; but the 
direction of twining of stems is invariable in the same species, and 
