154 



THE STEM PROPER 



PRACTICAL QUESTIONS 



r . Old Fort Moultrie near Charleston was built originally of pal- 

 metto logs ; was this good engineering or not? Why? 



2. Why is a stalk of sugar cane so much heavier than one of corn? 

 A green cornstalk than a dead one? (215.) 



3 . Explain the advantages of structure in a culm of wheat ; a stalk 

 of corn; a reed. (218.) 



4. Would the same quality be of advantage to an oak? Why, or 

 why not? 



5. Is it any advantage to the farmer that grain straw is so light? 



STEMS OF DICOTYLEDONS 



Material. — Twigs from one to three years old of almost any kind 

 of hard wood shoots ; elm, basswood, mulberry, leatherwood, and paw- 

 paw show the bast well ; sassafras, slippery elm, birthwort {Aristolo- 

 chia), and in spring, hickory and willow, show the cambium ; grape 

 and Trumpet vine the ducts. Have some twigs placed in red ink from 

 four to twelve hours before the lesson begins. Grape, peach, or hickory 

 will answer well for this purpose. 



219. Examination of a Typical Specimen. — Examine 

 carefully the outer surface of a young twig, not less than 

 one nor more than three years old, of any 

 convenient specimen. Notice the scars left 

 by the leaves of the season as they fell away, 

 and look for one or more little roundish 

 dots called leaf traces, that mark the points 

 where the iibrovascular bundles from the 

 leaf veins passed into the stem. The little 

 oblong or lens shaped corky spots that dot 

 the surface of a twig are called lenticels. 

 They are the breathing pores or ventilators 

 through which the air penetrates to the 

 Alternate inner parts of the stem. They usually 

 disappear on older branches, where the 

 outer bark is constantly breaking away and 

 sloughing off. Sometimes, however, they 

 are quite persistent, as in the peach, cherry, 

 and china tree. The characteristic markings of the birch 

 bark, which make it so ornamental, are due to the lenti- 



leaved twig of wal- 

 nut : t, terminal 

 bud; j,j, leaf scars; 

 tr, leaf traces; //, 

 lenticels. 



