74 THE STEM. 



181. The RHizoMA, or rootstock, is a prostrate, thickened, 

 rooting stem, either wholly or partially subteiTanean, often cov- 

 ered with scales, wliich are the rudmients of leaves, or marked 

 with scars, wliich indicate the insertion of former leaves, and 

 yearly producing both shoots and roots. Such is the thickened, 

 horizontal portion of the blood-root (Sanguinaria), sweet flag 

 (Calamus), and the bramble (Rubus). 



182. The CREEPER diflfers from the above only in size, consisting of slender 

 branches, exceedingly tenacious of life, extending horizontally in all directions, 

 and to considerable distances beneath the surface, sending out roots and branches 

 at intervals. The witch -grass (Triticum repens) is an example. Such plants 

 are a sore evil to the garden. They can have no better cultivation than to be 

 torn and cut in pieces by the spade of the angiy gardener, since they are thus 

 multiplied as many times as there are fragments. 



a. Kepent stems of this kind are not, however, without their use. Tliey fre- 

 quently abound in loose, sandy soil, which they seiwe to bind down and secure 

 against the inroads of water, and even of the sea itself. Holland is said to owe its 

 very existence to certain repent stems, by which its shores are apparently bound 

 together. Much of the suiface of that country is well known to be even below 

 the level of the sea. To protect it from inundation, dikes of earth have been 

 built, with immense labor, along the coast. These dikes are overspread A\'ith a 

 thick groAvth of such plants as the mat-grass, or Arundo arenaria, the Carex are- 

 naria, and the Elymus arenarius, by the innumerable roots and creepers of which 

 they are enabled to resist the washing of the waves. 



183. To AERIAL STEMS bcloug the following varieties; — cauhs, 

 runner, scape, vine, tnuik, sucker, offset, and stolon. 



184. Caulis (stem) is the term commonly applied to the aerial 

 stems of herbaceous plants, which are annual in duration, and 

 destitute of woody tissue. Caulescent and acaidescent are con- 

 venient terms, denoliug, the former the presence, and the latter 

 the absence of the caulis, or aerial stem. 



185. Runner. This is a prostrate, filiform stem, or shoot, ex- 

 tending itself along the surface of the ground, and tlu-o\ving out 

 roots and leaves at its extremity, which become a new plant, 

 soon putting forth new runners in its ttirn. Ex. straAvberiy^ 



18G. The SCAPE is a stem which springs from the summit of 

 the root, or rootstock, and bears the inflorescence of the plant, 

 but not its foliage. Ex. Sarracenia, daffodil, several species of 

 the Orchis, &c. The foliage of such plants is usually radical, 

 that is, springing from the root or subterranean stem. 



