122 



ORGANOGRAPHY. 



are so abundant at the base of the stem, that they sometimes 

 double or triple its thickness {fig. 13, ra), and hence give to 

 the lower part of such stems a conical form. The internal 

 structure of the root of acotyledonous plants in all essential cha- 

 racters resembles that of the stem. 



Forms of Roots. — When a root divides at once into a number 

 of slender branches or rootlets, or if the primary root is but little 

 enlarged, and gives off from its sides a multitude of similar 

 branches, it is called fibrous. Such roots occur commonly in 



Fig. 233. 



Fig. 234. 



Fig. 233. Fibrous root of a Grass. 



Fig. 234. Coralline root. 



annual plants, and may be well seen in annual Grasses {fig. 233), 

 and in bulbous plants {figs. 216 and 217). 



Coralline Root. — This name is applied to a root which consists 



Fig. 236. 



Fig. 235 



^ 



Fig. 233. Tubercular roots of an Orchis. Fig. 236. Palmated tubercules 



of an Orchis. 



