STRUCTURAL BOTANY. 89 



tached to it are sessile. When it is thick and covered 

 with crowded flowers, it takes the name of receptacle. 



The leaves of a flower -cluster are usually called bracts 

 and hractlets — the former being the leaves of the main 

 peduncle, at its base, and the latter, smaller ones, those 

 on the points of attachment, and on the pedicels (if there 

 are any) of the several flowers. The bracts are often so 

 minute as to escape detection, and sometimes early de- 

 ciduous. 



169. In order fully to understand the various sorts 

 of inflorescence, it is necessary to first consider the solitary 

 flower, which, in fact, represents the simplest form of 

 inflorescence. Such a single flower occurs either on the 

 summit of the stem, or in the axil of a leaf. 



170. Solitary terminal and solitary axillary flowers 

 represent the two plans of inflorescence, the indefinite 

 and definite, in the simplest possible form. 



We have indefinite, or indeterminate inflorescence, 

 when all the flowers spring from axillary buds ; and the 

 definite, or determinate, when they spring from terminal 

 buds. 



AA INDEFINITE INFLORESCENCE. 



171. Indefinite or indeterminate inflorescence is that 

 sort of inflorescence in which the flowers all spring from 

 axillary buds, w^hile the terminal bud, developing as an 

 ordinary branch, continues the axis indefinitely. 



The various modes of indefinite inflorescence run into 

 each other through intermediate gradations. 



173. The principal sorts of indefinite infloeescence 

 are, 1, clusters with pedicelled flowers — namely, the ra- 

 ceme, panicle, umbel, corymb, and thyrsus ; and 2, clusters 



