RHIZOMES 259 



Rhizome-forming Plants. Many herbaceous plants, 

 indeed the great majority of species, do not merely 

 form a single aerial shoot system which dies at the 

 end of the growing season, but, in addition to aerial 

 shoots, an underground or surface shoot or shoot system 

 which survives from one season to the next, and is 

 called a rhizome. The rhizome may be formed by the 

 whole epicotyl of the seedling plunging into the earth, 

 and growing horizontally instead of vertically upwards 

 to form an aerial shoot ; but in most cases the rhizome 

 is produced by an axillary bud near the base of the 

 aerial shoot growing out horizontally. Usually the 

 rhizome bears scale leaves (Figs. 40, B, 41, A, C, sc.l.) 

 which remain small and do not turn green, but some- 

 times it bears foliage leaves which grow up into the 

 air on long stalks. From the rhizome one or more 

 aerial shoots, usually bearing both foliage leaves and 

 flower buds, grow up into the air. Very often the 

 terminal bud of the rhizome turns up and produces 

 a single aerial shoot (Figs. 40, B, 41, B, a.s.), the growth 

 of the rhizome itself being continued by the growth 

 of one or more axillary buds. Aerial shoots also often 

 arise directly from axillary buds. 



At the end of the growing season the aerial shoots 

 with their foliage leaves die down, but the rhizome 

 remains alive in a dormant condition till the beginning 

 of the next growing season, when growth is renewed 

 from terminal and lateral buds and a fresh portion 

 of the rhizome and new aerial shoots are produced. The 

 older parts of rhizomes commonly die off and decay. In 

 countries like England, with comparatively mild winters, 

 the growth of the rhizome of many species continues 

 throughout the winter except during" periods of severe 

 frost, and new leaves and buds are^slowly produced, 



