KINDS OF STOREHOUSES 



33 



45. A multiplier onioii. 



77. KINDS OF STOREHOUSES. Short and much thick- 

 ened or swollen parts of roots or stems are known as 

 tubers. These may be stem tubers, as the potato, or 

 root tubers, as the sweet po- 

 tato (45). Most tubers are sub- 

 terranean. 



78. Many tubers are stem at 

 the top and root in the remain- 

 ing part : these are called crown 

 tubers, because the upper part 

 comes to the surface of the 

 ground, or is a crown. Leaves 

 and stems arise from the upper 

 part. Beet, radish, parsnip, 

 turnip, salsify, carrot, dahlia 

 roots, are examples. These 

 tubers are usually much longer 



than broad, and generally taper downwards. 



79. A much thickened part which is composed of scales 

 or plates is a bulb. The bulb may be scaly, as in the 



lily; or it may be tuni- 

 cated, made up of plates 

 or layers within layers, 

 as the onion. 



80. Small bulbs which 

 are borne amongst the 

 foliage or flowers are 

 known as bulblets. Such 

 are the "top onions," and 

 the little bulbs which the 

 tiger lily (Fig. 30) bears 

 on its stem. Bulbs which 

 grow around the main bulb or which are formed by the 

 breaking apart of the main bulb, are known as bulbels. 

 Many bulbous plants propagate by means of bulbels. The 



Fig. 44. 



46. Section of a multiplier onion. 

 Natural size. 



