172 THE STEM PROPER 



4. What is the diflference between timber and lumber? Between a 

 plank and a board? Between a log, stick, block, and billet? 



5. Is the outer bark of any use to a tree, and if so, what? (176, 

 191, 219.) 



6. Why does sapwood decay more quickly than heartwood? 



FIELD WORK 



Make a study of the various climbing plants of your neighborhood 

 with reference to their modes of ascent, and the effect, injurious, or other, 

 upon the plants they cling to. Note the direction of twining stems and 

 tendrils, and their various adaptations to their office. Consider whether 

 the twining habit might not lead to parasitism, especially in the case 

 of soft-stemmed twiners when brought into contact with soft-stemmed 

 annuals. Observe the various habits of stem growth ; prostrate, de- 

 clined, ascending, etc., and see what adaptation to circumstances can 

 be detected in each case. 



Notice the shape of the different stems met with, and learn to 

 recognize the forms peculiar to certain of the great families. Observe 

 the various appliances for defense and protection with which they are 

 provided, and try to find out the meaning of the numerous grooves, 

 ridges, hairs, prickles, and secretions that are found on stems. Always 

 be on the alert for transformations, and learn to recognize a stem under 

 any disguise, whether thorn, tendril, foliage, water holder, etc. 



Note the color and texture of the bark of the different trees you see, 

 and learn to distinguish the most important by it. Observe the differ- 

 ence in texture and appearance of the bark on old and young boughs 

 of the same species. Try to account for the varying thickness of the 

 bark on different trees and on different parts of the same tree. Farmers 

 are generally engaged in clearing and pruning at this season, and it will 

 probably not be difficult to get all the specimens needed among the 

 rubbish they are clearing away. Notice the difference in the timber 

 of the same species when grown in different soils, at different ages of 

 the tree, and in healthy and weakly specimens. 



