74 



ACADEMIC BOTANY. 



PART SECOND.— PHYSIOLOGY. 



LESSON XIV. 



PvOOT AND SUBTEEEANBAN STEM. 



142. The Eoot: 143. Axial; 144. Inaxial ; 145. Tuberous. 146. 

 Air-plants. 147. Adventitious Roots. 148. Parasites. 149, 150. The 

 Stem: 151. Bulb; 152. Corm ; 153. Ehizome; 154. Tuber. 



142. The Root is the organ of absorption. It imbibes 

 food materials, which it sends up to the stem and leaves ; 



there they are 



digested into 



food and sent 



back to be 



stored both as 



food and struc- 

 ture in the 



stem and root. 



Roots are of 



two kinds,' 



Axial and In- 

 axial. 



143. The 



Axial root 



has a strong 



central root, 

 called Tap-root; it 

 characterizes E x o - 

 gens. It has four 

 forms, — Conical, 



¥io. ST.— St., with rinrrot, • Villi form or Tio. 88.— a, Butterwort (Pin- 

 lvs.audfls.,of Mexi- '-'arror, J^ anjorril, m g„icula vulgaris) ; b, Beva.T^1^ &. 

 can .Jalap (Bcoganium Spmdlc-shaped, Kad- 



pwga),a,ioo. .^j^ _ Napiform, or turnip-shaped. Jalap 



(Fig. 87) ; Ramose, or branching, Butterwort (Fig. 88). 



144. Inaxial roots have no tap-root, on account of the 

 early decay of the radicle. They characterize Endogens, 



