290 VEGETABLE ORGANOGRAPHY. 



another according to the nature of the young shoots they 

 are destined to protect : some inclose branches furnished 

 only with leaves and devoid of flowers ; these are called 

 Leaf-buds : the others contain only bunches, umbels, 

 or heads of flowers, and are called Flower-buds ; 

 some contain, at the same time, leaves and flowers, and 

 for this reason are named Mixed Buds. The first are 

 generally recognized by their long pointed form; the 

 second, by being round ; and the last, by an intermediate 

 form. It is evident that the distinction between leaf 

 and flower buds is only possible in trees where the 

 flowers arise independently of the leaves, as in the 

 Cherry, Apple, &c, and that the mixed buds are the 

 only ones which can be found in the trees where the 

 flowers grow upon the same branches as the leaves. In 

 the first, the position of the two kinds of buds is 

 determined beforehand, and the period of development 

 of each frequently disturbs the usual order of their 

 evolution from the top to the bottom. 



As to the young shoots which proceed from each bud, 

 the development takes place from the base upwards, to 

 whichever class they belong : the scales of flower-buds 

 ought to be considered as the rudiments of bracts, and 

 in many respects these buds might be compared to 

 involucra; there are really no other differences than 

 that the floral buds are usually caducous, whilst invo- 

 lucra are ordinarily persistent: but there are many 

 intermediate cases in duration and appearance ; thus the 

 envelope which surrounds the flowers of Cornus mascula 

 and Aucuba is sometimes called bud, at other times in- 

 volucrum, and both terms are, in fact, equally applicable 

 to it. We might very well say, that the head of flowers 

 in the Compositse and Dipsaceae is a kind of bud. 



When the petioles of trees are dilated at their base 

 into a sheath, this surrounds the young shoots and often 



