184 



DEFINITE INFLOEESCENCE. 



short, and the flowers closely approximated, with a centrifugal expan- 

 sion, the inflorescence has a contracted cymose form, and receives the 

 name of fascicle. A similar inflorescence is seen in such plants as 

 Xylophylla longifolia (fig. 250). When the axes become very much 

 shortened, the arrangement is more complicated in appearance, and the 

 nature of the inflorescence is only indicated by the order of opening of 



the flowers. In labiate plants, as the 

 dead-nettle (Lamium), the flowers 

 are produced in the axil of each of 

 the leaves, and might be looked 

 upon as ordinary whorls, but on 

 examination it is found that the 

 central flower expands first, and from 

 its axis two secondary axes rise, and 

 the expansion is thus centrifugal. The 

 inflorescence is therefore a contracted 

 biparous cyme, the flowers being 

 sessile, or nearly so, and the clusters 

 are called verticillasters {verticillus, a 

 kind of screw). Sometimes, especially 

 towards the summit of a biparous 

 cyme, owing to the exhaustion of the 

 growing power of the plant, one of 

 the bracts only gives origin to a new 

 axis, the other remaining empty, and 

 thus the inflorescence becomes uni- 

 lateral, and further development is 

 arrested (fig. 271 h). 



A branching biparous cyme is 

 observed in the privet (fig. 272). In 

 this the primary floral axis a' gives rise to secondary axes a" a, along 

 its whole length. These, in a similar manner, produce tertiary axes, a", 

 which again dividing in a cymose manner, the whole inflorescence 

 acquires an appearance not unlike a bunch of grapes, and has re- 

 ceived from some the name of thyrsus. 



In the uniparous cyme a number of floral axes are successively de- 

 veloped one from the other, but the axis of each successive generation, 

 instead of producing a pair of bracts, produces only a single one. Here 

 the basal portion of the successive axes collectively forms an apparent 

 or false axis, and the inflorescence thus simulates a raceme. In the 

 raceme, however, we find only a single true axis, producing in succes- 



Pig. 272. Branching tiparoua cyme or thyrsus of Privet (lAgustrvm vidga/re). The primary 

 axis, a', gives oflf secondary axes, a" a", which are opposite to each other, and produce ter- 

 tiary axes, a'" of", which are diehotomous, and consequently end in small three-flowered 

 cymes, c c. Of the three flowers terminating these tertiary axes, the central one expands 

 first, the evolution of the others heing centrifugal. 



Fig. 272. 



