l88 METHODS IN TEACHING 



results place the cuttings in the sand in November or De- 

 cember. In the spring try rooting oleander and willow in 

 bottles of water. 



A modification of propagation by cuttings is known as 

 layering. A branch of the plant from which the cutting 

 is to be made is cut partly off and pegged down in a shal- 

 low trench. It is then covered with soil for a few inches 

 above and below the point where the cut was made. 

 Plants which refuse ordinarily to grow from cuttings root 

 easily by this method. If the branch to be rooted is part 

 of a tree, or if, for any reason, it can not be bent to the 

 ground, it can be layered by pegging it in a box of earth, 

 which is placed upon a support high enough for the pur- 

 pose. Very interesting, also, are the processes of budding 

 and grafting, so indispensable in horticulture. These are 

 very simple, easily taught, and of unquestionable value to 

 any pupil. 



The work of plants in the disintegration of rocks, both 

 by growth of roots into faults and seams of rock strata and 

 by the dissolving action of acid secretions 

 Soil Makers w ^ furnish material for experiment and 



discussion, as will also the work of the 

 roots of leguminous plants, clover, peas, etc., in furnishing 

 free nitrogen to the soil. Have pupils dig up roots of clover 

 and examine the nodules which stud them thickly. These 

 nodules contain bacteria which have the power of making 

 soil nitrogen from that in the air, thus making it available 

 for plant food. The importance of this work will be better 

 appreciated by pupils if they understand that, of the plant 

 foods, nitrogen is one of the most difficult to supply to 





