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, 

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

 ce.sses, as in some species of the Orchis. 



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

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

 writers call this variety moniliform {monile, a necklace). 



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

 5, PcBoiiia ; 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 tlie varieties already mentioned, we mny acid several others, which are 

 remarlcably distinguished by tlieir not being fixed in the soil. 



149. l^h.c floating root is peculiar to plants which float loosely 

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

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

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

 the mud, and there ripens its seeds. 



150. Aerial xoo\.% are those Avhich, 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, Those which are sent forth 



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