MONOCOTYLEDONS. 287 



Examine the swollen lower portion of the shoot, which 

 often lies about a foot below the surface of the soil. Tear 

 off the thin outer scales (leaf -bases) which surround it, and 

 note the white, sticky, fleshy scales which make up the 

 greater part of the swollen mass. Cut (1) transverse and 

 (2) longitudinal slices through this mass, and notice in 

 the latter the small disc-like stem from which all the 

 scales arise, and which bears roots on its lower surface and 



'ASCENDING STEM 

 WITH FOLIAGE LEAVES 



Figs. 109, 110. Scaly Bulb of Turk's Cap Lily. 

 109 (A), Entire ; 110 (B), Median Longitudinal Section. 



buds on its upper surface. This structure is a bulb (Figs. 109, 

 110). It differs from the corm of the Crocus chiefly in the 

 relatively smaller size of the stem, and in its investment by 

 thick fleshy scales, which contain large stores of reserve 

 food. In scaly bulbs (Lilies, Fig. Ill) the food-containing 

 scales simply overlap at their margins, whereas in tunicated 

 bulbs (Bluebell, Onion, Hyacinth) the outer leaves are large 

 and completely ensheath the inner portions of the bulb. 



The coloured membranous covering on the outside of such 

 bulbs is formed by the shrivelled remains of the food-scales 

 of a previous season. 



