248 TEXTBOOK OF BOTANY 



Bud scales. The buds of most trees and shrubs of the temperate 

 zones have external leaf -like scales, which are usually hard and fibrous 

 as are those in tlie buds of oak, elm, maple, and buckeye. Less frequently, 

 the buds are enclosed by stipules as are those of the tulip tree, magnolia, 

 and some viburnums. The scales are often hairy or sometimes covered 

 with wax and resins. These scales decrease transpiration from the tissues 

 in the bud but do not "protect" them from freezing. In some plants 

 there is a gradual transition from the bud scales on the outside to true 

 leaves on the inside of the bud. 



Nearly everyone has witnessed the opening of buds on shrubs and 

 trees in spring. Sometimes the hard scales on the outside of the bud are 

 pushed off by the enlargement of the inner scales and young leaves ( Fig. 

 82 ) . In other buds the scales may elongate somewhat, but in a short time 

 abscise and fall off. 



Composition of scaly buds. The composition of a scaly bud may be 

 recognized easily by removing the scales and other structures, or b\' 

 examining longitudinal sections of the bud, or, better still, by studying 

 unfolding buds in spring. Each bud contains the growing point of a 

 stem, the stem tip; in most buds leaves have begun to develop on the 

 stem tips. Such buds are vegetative buds (also called branch buds and 

 leaf buds) and from them develop the leaf-bearing segments of the 

 stems of the current season. A careful examination of perennial woody 

 stems will indicate that the number of young leaves in the bud cor- 

 responds with the number of leaf scars on each annual segment of stem 

 growth. What does that fact indicate? What exceptions have you seen? 

 Are all the leaves of a herbaceous plant, such as coleus, present in the 

 terminal bud at a given time? 



A similar examination of some buds of elm, forsythia, cherry, peach, 

 or soft maple will reveal a stem tip bearing young flowers, but no leaves. 

 These are the reproductive buds, which are also called flower buds and 

 fruit buds. Subsequent growth of these structures results in flowers and 

 fruits. In other buds, such as those of horse-chestnut, lilac, apple, and 

 catalpa, both flower clusters and leaves are present. Such buds may be 

 termed mixed buds. 



Composition of non-scaly buds. If we examine actively growing her- 

 baceous plants, we find that the buds are less conspicuous because of 

 their small size and the usual absence of bud scales. The leaves near the 

 growing stem tip are small; the youngest ones are folded about the 

 stem tip just as they are in scaly buds. A longitudinal section of a coleus 



