54 DESCRIPTIVE BOTANT. PART I. 



bark, is an organ of the same description as the branch 

 itself. " Spines " originate in the transformation of 

 leaves, &c. (see art. 78.). 



J{n/nierg. These are branches which trail along 

 the ground, striking root at intervals, where the buds 

 develop and give rise to young plants, as in the straw- 

 berry. 



Suckers are branches originating below the surface 

 of the soil, and their base in consequence soon emits 

 roots. Any branch may be made to assume this cha- 

 racter artificially, by confining a portion of it below the 

 surface ; as the horticulturist is aware when he forms 

 his " layers." 



(63.) Subterranean Stems and Branches. There are 

 some stems and branches, which, instead of rising up- 

 wards, continue under ground, and creep horizontally 

 below the surface of the soil. These are very generally 

 mistaken for roots, and are usually termed " creeping 

 roots ;" but they may readily be distinguished from 

 roots, if not by their internal structure, at least by their 

 external appendages. They are mostly furnished with 

 scaly processes, or other traces of a degenerated and 

 modified form of the leaves ; and they produce buds, 

 and often throw up branches which rise above ground ; 

 or else they themselves ultimately take a tendency up- 

 wards, and become true aerial stems ; a good example 

 of which occurs in the common reed (Phragmites cuiii- 

 mnnin, fig. 4(5.). The swollen rhizomata of this plant 

 runs among the turf of our fens, forming large tubes 

 through the masses cut for burning. They are furnished 

 at intervals with pale membranous scales, or rudimentary 

 leaves ; and fibrous roots are given off from all the knots. 

 So soon as the rhizoma takes an upward tendency, it 

 contracts its dimensions, and ultimately rises above ground 

 as a slender stem, invested with long green leaves. The 

 term " rhizoma or root-stalk," is equally applied to pro- 

 strate stems, as in the iris tribe, and in some ferns, where 

 the upper surface gives rise to the leaves, and the lower 

 to the roots ; and also to the completely subterraneous 



