THE STEM OF VASCULAR, PLANTS. 129 



Allium tataricum ; there are others, where it is short, 

 lying upon the surface of the ground, as Allium sejies- 

 cens; — lastly, in others it is reduced to a simple orbi- 

 cular disk, as in Allium cepa. 



The short and stunted stems are often difBcult to be 

 recognised, because they are found concealed under 

 ground, as we see it in the Garlic : the same pheno- 

 menon is presented among Ferns, some of which have 

 the stem strong and upright, like a tree, — for example, 

 Dicksoniu : others have it twisted, weak, and climbing, 

 as Ugena; lastly, there are others (and it is these alone 

 which grow in our climate,) \^•ith the stem creeping 

 along the surface of the ground, or even beneath it. 



This kind of subterranean stunted stem, having the 

 appearance of a root, has been called Rhizoma by Ker, 

 a name which signifies like a root: and it expresses its 

 nature very well. The stems of Nymphcea, the European 

 Ferns, the European species of Arum, and several kinds 

 of Garlic, have Rhizomata. Hcdwig gave the name of 

 Truncus superJiciaUs to stems lying horizontally upon 

 the surface of the ground, — as, for example, the Iris 

 germanica. 



The Salix herhacea sometimes presents this subter- 

 ranean position of the stem in a peculiar manner. This 

 little plant grows in the turf upon the Alps, the soil of 

 which is liable to be elevated by more rolling down from 

 above : the stem, which is very short, becomes covered 

 with earth each autumn, and in the spring it lengthens 

 to the surface of the soil ; so that, after some years, the 

 whole stem is buried in the earth, and only shows upon 

 the sui-face the herbaceous tops of its branches. When 

 it grows, or is cultivated, in a soil which does not become 

 elevated, the woody stem creeps along the surface ; and in 

 this case, one cannot see the reason why it is called the 

 Herbaceous Willow. 



VOL. I. K 



