160 CLASSIFICATION OF ROOTS AND STEMS 



perishing. To the ckister of roots thus resulting, although they are 

 really secondary, the term "multiple primary" has also been applied. 

 A true multiple primary root is of rare occurrence and does not exist 

 among drugs. 



Adventitious Roots.— AW roots which are not primary, or branches 

 thereof, and all branches of roots which are not de\'eloped in regular 

 order of succession, are called Adventitious. 



Place and Nature of Origin. — Subterranean and Aerial Roots. — As to 

 their place and nature of origin, roots are Subterranean when they 

 originate from points underground, whether from root or stem, and 

 Aerial when they originate from points above the surface, whether from 

 root or stem. A root may originate from an aerial point and afterward 

 fix itself in the earth, as the Brace-roots of maize. 



Fascicled Roots. — A number of approximately equal and similar 

 roots occurring in a cluster, especially if they be fleshy-thickened, are 

 denominated Fascicled. 



Fibrous Roots. — Roots existing in the form of a mass of thin, fiber- 

 like, approximately equal and similar elements are called Fibrous 

 (Fig. 446). 



Functions of Roots. — As to their functions, roots are known as Absorb- 

 ing, Fixing, and Storage roots. A root of one kind may give origin to a 

 branch of a different kind. 



Haustoria. — Absorbing roots of parasitical plants are frequently 

 greatly modified in structure to form Haustoria. 



Rhizoids. — Fixing roots are usually designated as Rhizoids. 



Storage Roots are usually much enlarged and possess a fleshy con- 

 sistency and characteristic forms (Figs. 441 to 443). 



Tubercles. — When only a limited portion of a root is fleshy-thickened, 

 so as superficially to resemble a tuber, it is called a Tubercle, as the 

 Jalap (Fig. 437). Care should be taken not to confuse this technical 

 meaning of the term with its common use as designating a small tuber. 



Forms of Roots. — As to their form, roots are simple, when they do not 

 branch, or Branched, Cylindrical, Terete (which includes the cylindrical 

 and that form which differs only in that it tapers), Xapiform, when 

 taking the form of a short, broad turnip (Fig. 441), Fusiform when 

 spindle-shaped, as some radishes (Fig. 442), Conical or Cone-shaped 

 (Fig. 443), Capillary when very thin, long and 'hair-like. 



Consistency of Roots. — Woody and Fleshy Roots. — As to consistency, 

 they are denominated as Woody and Fleshy. By "fleshy" or "non- 

 woody" we do not mean that wood tissue is entirely lacking, but rather 



