FORMS OF SCALE-STEMS. 79 



232. Repent stems of this kind are not, however, without their nse. They frequently 

 abound in loose, sandy soil, which they serve to bind and secure against the inroads of 

 the water and even the sea itself. Holland is said to owe its very existence to the repent 

 stems of such plants as the Mat-grass (Arundo arcnaria 1 ), Carex arenarius, and Klymus 

 arenarius, which overrun the artificial dykes upon its shores, and by their innumerable 

 roots and creepers apparently bind the loose sand into a firm barrier against the washing 

 of the waves. So the turf^ chiefly composed of repent Grass-stem?, forms the only secu- 

 rity of our own sandy or clayey hills against the washing rains. 



233. THE RHIZOME OR ROOT-STOCK differs from the creeper 

 only in being shorter and thicker, having its internodes but par- 

 tially developed. It is a prostrate, fleshy, rooting stem, either 

 wholly or partially subterranean, often scaly with the bases of 

 undeveloped leaves, or marked with the scars of former leaves, 

 and yearly producing new shoots and roots. Such is the fleshy, 

 horizontal portion of the Blood-root, Sweet-flag, Water-lily, and 

 Bramble (the latter hardly different from the creeper). 



234. The growth of the rhizome is instructive, marking its peculiar character. Each 

 joint marks the growth of a year. In Spring, the terminal bud unfolds into leaves and 

 flowers, to perish in Autumn a new bud to open the following Spring, and a new inter- 

 node, with its roots, to abide several years. The number of joints indicates, not the age 

 of the plant, but the deslined age of each intcrnode. Thus if there are throe joints, we 

 infer that they are triennial, perishing after the third season, while the plant still grows on 



258 



258. Rhizoma of Solomon's Seal (Polygonatnm multiflorum). a. Frajrment of the first year's growth, 

 ft, the second year's growth; r, growth of the third year; <1, growth of the present (fourth) year, bearin,' 

 the stem, which, on decaying, will leave a scar (seal) like the rest. 2^9, Premorse root of Trillium 

 erect urn. 



235. THE PREMORSE ROOT-STOCK, formerly described as a root, 

 is a short, erect rhizome, ending abruptly below, as if bitten 

 square off (praemorsus). This is owing to the death of the 

 earlier and lower internodes in succession, as in the horizontal 

 rhizome. Scabius, Viola pedata, and Benjamin-root (Trillium) 

 are examples. 



236. CROWN OP THE ROOT designates a short stem with con- 

 densed internodes, remaining upon some perennial roots, at 01 



