CHAP. XVI VEGETATIVE REPRODUCTION 79 



VII. Plants having underground stems which branch, in- 

 crease in number by the dying away of the older portions 

 of the stem. When the dying portion reaches a place where 

 a branch is situated, the union between the two parts is 

 broken and instead of one plant we have two. After this 

 has been repeated several times, there are several plants, all 

 from the same original stock. 



To realize how this may happen, examine the slender 

 root-stock of some Mint or Grass and notice : 



1. The branches, which may be numerous or may be few. 



2. The nodes and internodes. 



3. The buds at the nodes, which may develop into lateral 



branches. 



4. The terminal buds at the ends of the branches. 



5. How the root-stock is dying away at the other end of the 



root-stock. 



6. Make sketches to show these points. 



VIII. Examine the underground portions of Iris, notice 

 how it is multiplied (as described in VII) and make dia- 

 grams to show it. 



IX. Examine slips or cuttings of Pelargoniums, English 

 Ivies, or Willows, which have been planted in moist sand 

 for several weeks. Make sketches and describe what has 

 happened. What are the advantages of propagating a plant 

 by cuttings over propagating by seed? Write your answers. 



X. Examine leaves of Bryophyllum (or leaf-cuttings of 

 some species of " tuberous Begonia ") which have been 

 lying upon moist sand. Notice and sketch the buds formed 

 at the notches in the margin of the leaf (or at the cut ends 

 of the ribs of the leaf of the Begonia) sketch and label. 



