ROOTS. 



65 



tumors, situated at the base among the fibres. Ex. Orchis. 

 This root must be distinguished from the tuber, which, hke the 

 potatoe, uniformly bears buds, and is now classed among stems. 



a. A palmate (hand-shaped) root is a variety of the tuberous, 

 where the knob is separated below into short, thickened pro- 

 cesses, as in some species of the Orchis. 



b. A gramdated root consists of many small tubercular knobs, 

 connected by fibres, as seen in the common wood sorrel. Some 

 writers call tliis variety tnoniliform (nionile, a necklace). 



FIG. 21. — Forms of the root ; — 1, Raphanus ; 2, Brassica rapa ; 3, Scabiosa ; 4, Poa ; 

 5, Pseonia ; 6, Dahlia. 



148. All the above forms of fleshy roots appear to be reser- 

 voirs where the superabundant nutriment secreted by the plant, 

 is accumulated and kept in store for the following year, or for 

 the time of flowering. 



a. To the varieties already mentioned, we may add several others, •which are 

 remarkably distinguished by their not being fixed in the soil. 



149. The Jloating root is peculiar to plants which float loosely 

 upon the surface of the water. Ex. Lemna, CalHtriche. The 

 latter, called water starwort, floats upon the surface only until 

 flowering, after wliich it sinks to the bottom, fixes its roots in 

 the mud, and there ripens its seeds. 



150. Aerial xoots are those which, instead of originating from 

 portions of the plant beneath the surface of the ground, are pro- 

 duced from some portion in the open air. Of these roots, seve- 

 ral varieties are remarkable. 1st, Tliose wliich are sent forth 



