GROWTH AND WORK OF PLANTS 



which extend from the stem into the petiole of the leaf. Scat- 

 tered over the surface of the shoot are numerous minute, 

 grayish or dull white elevations, the lenticels. 



113. Shoots of the lilac. The shoots of the lilac have the 

 same arrangement of the lateral buds and leaf scars 

 as those of the horse chestnut. They are opposite 

 and in pairs, and each pair alternates in position 

 with the pair above and below. The leaf scar is 

 much smaller and semi-lunar in shape. The outer 

 bud scales are brown, while the inner ones are green, 

 and some of the intermediate ones have brown tips 

 and green bases. There is one interesting point of 

 difference, however, between the shoots of the lilac 

 and those of the horse chestnut. The shoot appears 

 to have a pair of terminal buds which stand slightly 

 divergent. There is a leaf scar at the base of each 

 one which shows that these buds are axillary, i.e., 

 they arise in the axils of the leaves. They are, there- 

 fore, axillary terminal buds. This would indicate 

 that the true terminal bud was subordinate. This 

 is true. If we search carefully between the pair of 

 axillary terminal buds there is found a minute dead 

 terminal bud, or the scar left where it has fallen 

 away. This indicates that the shoots of the lilac 

 have indefinite or indeterminate growth. Those of 

 the horse chestnut have determinate growth. The 

 pair of axillary terminal buds of the lilac form, the 

 following year, a pair of shoots which diverge, or 

 fork. Some of these buds, however, are flower 

 buds, as can be determined by dissecting them. 



J 



114. Shoots of the elm. The elm represents 

 still another type of shoot, as shown by the position of the buds. 

 The buds are alternate, and are situated in two rows on opposite 

 sides of the shoot. The shoots are more or less zigzag in out- 

 line, the buds situated at the angles thus formed. On the 

 ascending or horizontal shoots the rows of buds are lateral, so 



Fig. 63. 

 Shoot of lilac 



