64 LABORATORY PRACTICE 



CHAPTER XII 



CLIMBING PLANTS 



IN our work upon stems (compare Chapter IV), we 

 found that one of the functions or uses of the stem was to 

 support the leaves and to carry them up into the air. 



When we examine plants as regards height of stem, we 

 find that this varies from almost nothing to several hundred 

 feet. We find also, as a general rule, that the higher the 

 plant rises into the air, the stouter the stem becomes, until 

 we have such stems as the trunks of trees. 



There is one set of plants, however, which do not follow 

 this rule. They rise above their neighbors to obtain the air 

 and sunshine they covet, while still possessing weak and 

 slender stems. Such are the plants which have climbing 

 habits. 



I. Take a plant (or the upper portion of a plant) of the 

 Hop or of Manettia. Examine it carefully and notice : 



1. The very slender stem. 



2. That it has entwined itself spirally about a slender 



support. 



3. That it twines about the support with the sun or from 



right to left (as one faces it). 



4. The tip, usually extending out at nearly right angles to 



the support, and then curving abruptly. 



5. Make a sketch to show these points. 



