78 



IN DETERMINATE irvri^OEESCENCE. 



These axes themselves aie called 

 radii. 



The preceding varieties follow the 

 centripetal order of flowering, that is, 

 the flowers farthest from the centre 

 expand first. 



But there are others of the deter- 

 minate form which follow the cen- 

 trifugal order, that is, the central or upper ones expand 



first, and the external or lower ones 

 last. When the secondary axes 

 start from the same point, as in 

 the umbel, but these dichotomizing 

 producing tertiary branches, with a 

 flower in the axil, we have a cyme, 

 (fig. 82.) 



A glomerule is similar to a capit- 

 ulum, but diflfers from it as a simple 

 ^"'umbel does from a compound one, 

 that is, it is composed of numerous 

 capitula, enclosed in a common in- 

 volucre as in the Echinops or Globe Thistle. 



A Fascicle is of the centrifugal order of expansion, and is. 

 in other respects, similar in appearance to the umbel, but has 

 the arrangement of the cyme with the flowers more compact 

 and branches shorter. The Pink tribe affords examples. 



Indeterminate Injtorescence, 



88. This form of infloresence is characterized by the con- 

 tinued growth of the primary 

 axis, while the secondary and 

 tertiary are arrested. 



The Spike is of this form and 

 go is supposed to be produced by 

 the continued elongation of the 

 primary axis, while the seconda- 

 ry, having no power of elonga- 

 tion, produces sessile flowers 

 along a common axis, which con- 

 stitutes the spike, (fig. 83,) as in 

 the Plantains. 



When sessile flowers are arran- 

 ged on a filiform rachis, which 

 falls off after flowering, it is called an ament 



