THE ROOT 



223 



Fiof. 204. — Fibrous roots. 



3. In grasses and other monocotyledons the main root soon 



perishes, and then adventitious roots, produced from the lowest or 



any one of tjie lower nodes of the stem, 



take lip the functions of the main root 



and its side-roots. Such adventitious 



roots may be formed from other parts 



of the plant also, e.g., from underground 



stems (Canna, Lotus, 

 Potato), from stolons 

 (Hydrocotyle), from 



creeping stems (Ipom?ea batatas), from 

 branches (Banyan), from cut stems (Lantana, 

 Rose), or in certain plants even from leaves 

 (Bryophyllum, Begonia). 



4. Some types of roots do not penetrate 

 into the soil. As clinging roots they fasten 

 the plant to its support (Pepper, Pothos 

 scandens) ; as aerial roots they absorb the 

 atmospheric moisture (several epiphytical 

 orchids) ; as parasitical roots they sink their 

 suckers into the tissue of the foster plant; 



and as breathing roots they help the Mangrove trees to get oxygen 



for their roots in the 



marshy soil in which they 



cannot breathe. 



5. In some plants 



roots become storing places 



for food material and are 



then swollen. So the 



thickened tap-root of the 



Carrot and of the Radish, 



or the swollen adventitious 



roots of Asparagus, of the 



Sweet Potato, and the 



bulbous roots of some 



terrestrial orchids (Habe- 



naria rotundifolia, p. 159). 



Fig. 205. — Parasitical 

 root of Mistletoe. 



Fig. 206. — Thickened side-roots of Asparagus. 



