84 



ELEMENTS OF STRUCTURAL BOTANY. 



compact, as in the Grape and Lilac, it is what is called 

 a thyrse. 



124. Of determinate inflorescence the chief 

 modification is the cyme. This is a rather flat-topi)ed 

 cluster, having something the appearance of a com- 

 pound corymb, but easily distinguished by this peculi- 

 arity, that the central blossom opens first, then those at 

 the ends of the first set of branches of the cluster, then 

 those on the secondary branches, and so on until the 

 outer buds are reached. The Elder, Dogwood, and St. 

 John's Wort furnish good examples of the cymose 



Fig. 137. 



structure. Fig. 137 s'hows a loose open cyme. 



125. It has already been pointed out that cauline 

 leaves tend to diminish in size towards the upper part 

 of the stem, where the flowers are found. Such re- 

 duced leaves, containing flowers in then- axils, are called 

 bracts. In the case of compound flower-clusters, this 

 term is limited to the leaves on the peduncle, or main 

 stem, the term hractlct being then applied to those oc- 

 curring on the pedicels or subordinate stems. In the 



