FALLING OF THE LEAF 



!>7 



evergreen. Most leaves fall by breaking off at the lower 

 end of the petiole with a distinct joint or articulation. 

 There are many leaves, however, which wither and hang 



138. Elliptic leaf 

 of purple beech. 



l:jU. Ovate serrate leaf 

 of hibiscus. 



14ii. < >rliicular lolicil leaves. 



cn the plant until torn off by the wind : of such ;ir- the 

 leaves of grasses, sedges, lilies, orchids, and other plant > 

 known as monocotyledons (Chap. XXIII). Most leaves 

 of this character are parallel -veined. Consult 439. 



205. Leaves also die and fall from lack of light. Qbi 

 serve the yellow and weak leaves in a dense tree-top or in 

 any thicket. Why do the lower leaves 



die on house-plants? Note the carpel 



Of needles llllder the pines. All I'ViT- 



greens shed their leaves after a time. 

 Counting back from the tip of a pine 

 or spruce shoot, determine how many 

 years the Leaves persisl (Fig. 14.")). 

 In some spruces a few leaves maj be 

 found on branches ten or more years 

 old. Leaves usually persisl longesl 



in the lightest position- (Fig. 77). ML Truncate leaf of tulip-tree 



206. Although the forms and positions of leaves often 

 have direct relation to the places and conditions in which 



