ROOTS. 



29 



strength of the supplies of ready-made sap which it obtains 

 from the host. 



43. Forms of Roots. — 

 The primary root is that 

 wliich proceeds like a 

 downward prolongation 

 directly from the lower 

 end of the caulicle. In 

 many cases the mature 

 root-system of the plant 

 contains one main portion 

 much larger than any of 

 its branches. This is 

 called a taproot, Fig. 16. 



Such a root, if much 

 thickened and fleshy, 

 would assume the form 

 shown in the carrot, pars- 

 nip, beet, turnip, salsify, 

 or radish. Some plants 

 produce multiple primary 

 roots, a cluster proceeding 

 from the lower end of the 

 caulicle at the outset. 



Roots of grasses, etci, 

 are thread-like, and known 

 as fibrous roots, Fig. 17. 

 If such roots become thick- 

 ened like those of the 

 dahlia. Fig. 18, they are 

 known as fascicled roots. 



These often closely re- 

 semble tubers, but they 

 may be distinguished from them 



Fig. 



15. — Dodder (a European species) Parasi- 

 tic on tlie Willow. 



The plant is seen encircling a willow twig, into 

 which it sends roots from the warty inner 

 surface of its coils. 



b, scale-like leaves ; Bl, flower-cluster. 



At the left is shown the manner in which the 

 parasite Cus encircles the host-plant W. 



The parasitic roots or haustoria H penetrate 

 into tlie parenchyma of theharlc and into 

 the fibro-vascular bundles, attaching them- 

 selves to the various kinds of tissue, v, c, s, 

 which they find in these. 



At the right are seedling dodder plants, the 

 longest one growing at the tip from nourish- 

 ment which it procures from the dying end 

 next the root. 



by their mode of origin. 



