24 



OEGANOGBAPEF. 



root) is very common, as in the Mint, Coucli-grass, etc. ; it 



is merely a root-stock, or stem growing under the surface 



of the ground, pro- 

 ducing roots, also 

 leaf-scales and buds 

 (Fig. 17). A tuber 

 is a thickened por- 

 tion of a root-stock. 

 The Potato is the 

 commonest example, 

 the " eyes" being 

 buds (Fig. 18). The 

 corm is a very 



short, thickened root-stock, with roots below and buds 



above. 



23. The bulb is an extremely short root-stock, pro- 

 ducing, like the corm, roots from the under side. It is 



covered with leaves, or the base of leaves, in the form of 



thickened scales. If the latter are broad, and cover all that 



is within, the bulb is said 



to be coated (Fig. 19), or 



tunicated (Lat. tunica, 



covering). But if the 



scales are narrow and 



separate, as in the Lily, 



the bulb is said to be 



scaly (Fig. 20). The 



small buds above ground, 



as in the axils of some Lilies, etc., are called bulblets. 



The bulb, like the corm and tuber, is a reservoir of 



Fig, 18. Potato tuber (i) ; r, roots; j*, stems. Fig. 19. A coated bulb. Fig. 20. 

 A scaly bulb. 



