THE STEM, OR ASCENDING AXIS. 



into the air. The witch-grass (Triticum repens) is an example. Such 

 plants are a sore evil to the garden. They can have no better cultiva- 

 tion than to be torn and cut to pieces by the spade of the angry gar- 

 dener, since they are thus multiplied as many times as there are 

 fragments. 6 & 



Fig. 51. Creeper of "Nimble Will," or witch-grass; a, Bud; bb, Bases of culms. 



182. Utility. Repent stems of this kind are not, however, without their use. 

 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 arenaria), 

 Carex arenarius and Elymus arenarius, which overrun the artificial dykes upon it3 

 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-stems, forms the only security of our own sandy or clayey hills 

 against the washing rains. 



183. The rhizome or root-stock differs from the creeper only in 

 being shorter and thicker, having its internodes but partially developed. 

 It is a prostrate, fleshy, rooting stem, either wholly or partially subter- 

 ranean, often scaly with the bases of undeveloped leaves, or marked 

 with the scars of former leaves, and yearly producing new shoot3 and 

 roots. Such is the fleshy, horizontal portion of the blood-root, sweet- 

 flag, water-lily, bramble (the latter hardly different from the creeper). 



184. 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 int© 



52 52 o 



Fig. 52. Rhizoma of Solomon's-seal (Polygonatum multiflora) n, Fragment of the first year's 

 growth ; b, the second year's growth ; c, growth of the third year ; d, growth of the present 

 (fourth) year, bearing the stem which, on decaying, will leave a sear (seal) like the rest. 53. Pre- 

 morse stem of Trillium. 



