OEGANS OF NUTRITION. 



Ill 



covering or tunic to them, and hence the name Umicated or 

 coated, which is applied to it. In the scaly, or naked bulb as 

 it is also called {fig. 216), the whole of the scales of which it 

 is composed are thick and fleshy, and overlap each other like 

 the component leaves of an ordinary bud. 



In the axils of the leaves of certain plants, such as some 

 species of Lily {fig. 218), the Coralwort {Dentaria bidbifera), 

 and Pilewort {Ranunculus Ficaria), small conical or rounded 

 •fleshy bodies are produced, which are of the nature of bulbs, 

 and are hence called Aerial bulbs from their position, or from 

 their small size, bulbils or bulblets. They differ from ordi- 

 nary buds in their fleshy nature, and by spontaneously sepa- 

 rating from their parent, and producing new individuals when 

 placed under favourable circumstances. These aerial bulbs are 

 not confined, as is the case with true bulbs, to Monocotyledo- 

 nous Plants (as may be seen by the examples given). 



The young bulbs which are developed in the axils of the 

 scales of subterranean bulbs either remain attached to their 

 parent, which they commonly destroy by absorbing all its 

 stored-up nutriment ; or they become separated in the course of 

 growth, and form independent plants. 



d. The Corm, — This form of stem, like the true bulb, is only 

 found in Monocotyledonous Plants, as, for example, in the Colchi- 



Fig. 219. 



Fig. 220. 



Fig. 219. Corms of Crocus sativtis. a, b. Tlie new corms, arising from c, 

 the apex of the old or parent corm. Fig. 220. Section of the former. 



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cum {fig. 221), and Crocus {figs. 219 and 220). It is an enlarged 

 solid subterranean stem, of a rounded or oval figure, and com- 

 monly covered externally by thin membranous scales. By some 

 botanists it is considered as a kind of bulb, in which the stem 

 or axis is much enlarged, and the scales reduced to thin mem- 

 branes. Practically a corm may be distinguished from a bulb 

 by its solid nature, the bulb being formed of imbricated scales. 

 The corm is known to be a form of stem by producing from its 



