184 THE GROWTH OP ROOTS AND STEMS. 



rhizonie, the green foliage-leaves being borne upon erect 

 aerial shoots. Numerous adventitious roots are present, 

 which grow out mainly from the under-surface of the rhizome, 

 and usually near to the bases of scale leaves that is, from the 

 "nodes." Rhizomes often branch to a slight extent, and each 

 branch when separated, either artificially or by the decay of 

 the older parts, is capable of forming a new plant. 



Year by year a rhizome travels to fresh portions of the 

 soil, often slanting upwards, but in that case the new parts 

 are dragged down to the same depth by the contraction of 

 the roots. 



As examples, you should study the rhizomes of various 

 Grasses (e.g. Couch-grass) and Sedges (Fig. 60), Iris, Solo- 

 mon's Seal (Fig. 113), Wood Sorrel, Wood Anemone. 



Fig. 60. Rhizome of Sedge (Carex) in Summer. 

 I) last year, (II) this y 

 IV) year next but one. 



Flowering shoots of (I) last year, (II) this year, (III) next year, 



221. The stem-tuber is a swollen underground branch 

 containing stored food-materials and bearing buds. Ex- 

 amples are afforded by Potato (Art. 362) and Jerusalem 

 Artichoke. 



222. The corm is a shoot whose basal stem portion 

 becomes swollen and filled with food-materials after flowering 

 has taken place. The COITUS of two or three years often 

 stick together so as to produce what may be regarded as a 

 condensed form of rhizome bearing axillary buds either 

 laterally (Colchicum) , as in a creeping rhizome, or on the 

 upper surface (Crocus), as in an upright rhizome or "root- 

 stock." 



