ROOTS. 73 



of fibres have been called fibrils, or little fibres, and if 

 you looked at them through the microscope you 

 would, in some cases, see upon them still finer 

 threads or root hairs (cf. Fig. 29 h, p. 34). 



As you look at these fibrous roots you can notice 

 another difference between roots and stems. As 

 roots are different from stems in not having any 

 leaves (p. 16), so also they do not branch, like stems 

 do in any regular order. 



And there is another thing to notice. Sometimes a 

 root has its fibres much enlarged into fleshy swellings 

 or tubercles * as in the garden dahlia. Do not confound 

 these tubercles or swollen root fibres with the tubers 

 or swellings of underground stems. The tubercles do 

 not break into bud as the tubers do. If you can get 

 a gardener to show you some dahlia stocks when he 

 is planting them in the spring time, you will see a 

 good example of these tubercles, and then notice how 

 the new shoots are coming from the old stem stock, 

 and none from the tubercles alone. These tubercular 

 roots are often called nodulose, i.e., knotty. f When 

 you know more plants by name you will be able to 

 find such a root in the common dropwort (Spircea 

 filipendula], and to compare with it that of the water 

 hemlock dropwort (CEnanthe crocatd}. In some 

 plants these swellings are all along the root fibres, so 

 that they look like strings of oval beads, % and if you 



* From the Latin " tubtrculus" " tuber" swelling, bump, 

 t From the Latin " nodus" a knot. 



\ That kind of root is called moniliform, from the Latin " 

 a necklace. 



