74 THE STKM. 



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

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

 ered with scales, which are the rndiments of leaves, or marked 

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

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

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

 (Calamus), and the bramble (Rubus). 



1 82. The CEEEPEK differs 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 -switch-grass (Triticum repens) is an example. Such plants 

 ai'e 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 angry gardener, since they are thus 

 multiplied as many times as there are fragments. 



«. Repent stems of this kind are not, however, without their use. They fre- 

 quently abound in loose, sandy soil, which they sei-ve 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 surface of that country is well known to be even below 

 the level of the sea. To protect it fi-om inundation, dikes of earth have been 

 built, vdth immense labor, along the coast. These dikes are overspread with a 

 tliick growth 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 wasliing of the waves 



183. To AERIAL STEMS belong the following varieties; — caulis, 

 ruiiner, scape, vine, trunk, 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 acaulescent are con- 

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

 the absence of the cauhs, or aerial stem. 



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

 tending itself along the surface of the ground, and throwing out 

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

 soon putting forth new runners in its tiun. Ex. strawberry. 



186. 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 fohage of such plants is usually radical, 

 that is, springing from the root or subterranean stem. 



