STEMS 51 



64. Twig of Poplar. — Sketch a vigorous young twig of poplar (or 

 of hickory, magnolia, tulip tree) in its winter condition, noting par- 

 ticularly the respects in which it differs from the horse-chestnut. 

 Describe in writing any facts not shown in the sketch. Notice that 

 the buds are not opposite, nor is the next one above any given bud 

 found directly above it, but part way round the stem from the 

 position of the first one. Ascertain, Vjy studying several twigs and 

 counting around, which bud is above the first and how many turns 

 round the stem are made in passing from the first to the one directly 

 above it. 



Observe with especial care the difference between the poplar and 

 the horse-chestnut in mode of branching, as shown in a large branch 

 provided for the study of this feature. 



65. Relation of Leaf Arrangement to Branching.^ — This 

 difference depends on the fact that the leaves of the horse- 

 chestnut were arranged in pairs on opposite sides of tlie 

 stem, while those of the jDoplar were not in pairs. Since 

 the buds are found at the upper edges of the leaf -scars, and 

 since most of the buds of the horse-chestnut and the poplar 

 are leaf-buds and destined to form branches, the mode of 

 branching and ultimately the form of the tree must depend 

 largely on the arrangement of leaves along the stem. 



66. Opposite Brajiching. — In trees, the leaves and buds 

 of which are opposite, the tendency will be to form twigs 

 in four rows about at right angles to each other along the 

 sides of the branch, as shown in Fig. 24. 



This arrangement will not usually be perfectly carried 

 out, since some of the buds may never grow, or some may 



^ The teacher in the Eastern and Middle States will do well to make con- 

 stant use, in the study ol branches and buds, of Newell's Outlines of Lessons 

 in Botany, Part I. The student can observe for himself, with a little guid- 

 ance from the teacher, most of the points which Jliss Newell sugg&sts. If the 

 supply of material is abundant, the twigs employed in the lessons above 

 described need not be used further, but if material is scanty, the study of buds 

 may at once be taken up. (See also Bailey's Lessons with Plants, Part I.) 



