SECTION 7.] 



SPECIAL LEAVES. 



63 



Beans, give faint indications of service as foliage also, chiefly in vain. Still 

 others, as in the Pumpkin and Flax, having served for storage, develop 



into the first efficient foliage. Compare 

 11, 22-30, and the accompanying figures. 



166. Leaves as Bud-Scales serve to 

 protect the forming parts within. Hav- 

 ing fulfilled this purpose they commonly 

 fall off when the shoot develops and 

 foliage-leaves appear. Occasionally, as 

 in Fig. 170, there is a transition of bud- 

 scales to leaves, which reveals the nature 

 of the former. The Lilac also shows a 

 gradation from bud-scale to simple leaf. 

 In Cornus florida (the Flowering Dog- 

 wood), the four bud-scales which through 

 the winter protect the head of forming 

 flowers remain until blossoming, and then the base of each grows out into 



Fio. 170. Series of bud-scales and foliage-leaves from a developing bud of the 

 Low Sweet Buckeye (JSsculus parviflora), showing nearly complete gradation, from 

 A scale to a compound leaf of five leaflets; and that the scales answer to reduced 

 petioles. 



T?ig. 171. Shoot of common Barberry, showing transition of foliage-leaves to 

 spines. 



