UNDERGROUND STEMS 131 



Place a cutting of rose geranium or of coleus in a pot of 

 moist sand. As soon as the roots begin to form, examine 

 the stem with a lens to see from what portion they spring 



271. — New stocks with adventitious roots produced by layering. 



— whether from near the circumference, or from the cen- 

 ter. What part of the stem should you infer from this, is 

 most actively concerned in the work of growth ? 



PRACTICAL QUESTIONS 



1 . Do the adventitious roots of sucli climbers as ivy and trumpet 

 vine draw any nourishment from the objects to which they cling? 



2. How do you know this? 



3. Do they injure trees by climbing upon them ; and if so, how? 



4. What is the use of the aerial roots of the scuppernong grape? 



5. Is the resurrection fern (Polypodium incanum) a parasite or an 

 air plant? 



5. On what plants in your neighborhood does mistletoe grow most 

 abundantly ? Dodder ? 



7. Is mistletoe injurious to the host? 



8. Name some plants that are propagated mainly, or solely, by roots 

 and cuttings. 



UNDERGROUND STEMS 



Material. — Underground stems of couch grass, nut grass, violet, 

 iris, or any rootstocks obtainable. In cities, if nothing better is to be 

 had, some dried orris root or calamus might be obtained from a drug- 

 gist. Any kind of tuber, such as potato, artichoke, Madeira vine, etc. 

 A sweet potato. A scaly lily bulb and one of onion or hyacinth. Pota- 

 toes and sweet potatoes treated with red ink. 



188. Rootstocks. — So like fleshy roots are certain thick- 

 ened underground stems that it is not always easy to dis- 

 tinguish between them. So long as the stem remains above 



