118 COMPOUND ORGANS OF PLANTS. 



summit of the tertiary or any other succeeding axis which 

 may be developed. In this case, therefore, since the flower 

 terminating the growth of the primary axis is the oldest, 

 and consequently the first to expand, the other flowers 

 expanding in succession in proportion as they are removed 

 farther from the centre, the expansion of the flowers is 

 necessarily centrifugal, or from the centre to the circum- 

 ference. 



This mode of inflorescence is termed a cyme, and as the 

 divisions in this case always take place by two, it is called a 

 dichotomous cyme, ($t*a, two ways, and -tip,, I cut.) If, 

 instead of two, three whorled leaves or bracts developed floral 

 axes in a similar manner, the cyme would be trichotomous, 

 (fpt'^a, in three ways.) 



The inflorescence has received different names according to 

 the different modes in which the flowers are arranged on the 

 axis, and the extent to which that axis is developed. 



The following are the leading forms assumed by the indefi- 

 nite or indeterminate inflorescence. If the axillary flowers are 

 without a peduncle or flower stalk and sessile along the 

 common axis, they form a spike, as in the Plantain, (Fig. 

 21.) If, on the contrary, the axillary flowers are supported 

 on a peduncle under the same circumstances, they form a 

 raceme, as in the wild cherry, (Fig. 22.) 



If the floral axis of a spike is shortened by the non-develop- 

 ment of the floral internodes, a capitulum or head is produced, 

 as in * Cephalanthus occidentalis, (Fig. 23.) Sometimes the 

 capitulum becomes partially elongated into a spike as it grows 

 older, as in Sanguisorba and many species of Clover. The 

 shortened axis of a head is called a receptacle. ' ^ 



Frequently, instead of being globular as in Cephalanthus. 



