104 INFLORESCENCE. 



eences, are centripetal, while the general inflorescence is centri- 

 fugal, that is, the central head is developed before the lateral 

 ones. But in the Labiatse the partial inflorescences (verticilas- 

 ters, 309) are centrifugal, while the general inflorescence is 

 centripetal. 



296. Of centripetal inflorescence the principal varieties are, 

 ^e spike, raceme, ament, spadix, corymb, umbel, l:ead^ 



panicle, and thyrse. 



297. The spike is an inflorescence consisting of several ses- 

 sile flowers arranged along a common peduncle (racliis). Ex, 

 Plantago, Verbascum. ■ 



298. The kaceme is the same as the spike, but having the 

 flowers raised on pedicels, each being axillary to a bract, and 

 blossoming in succession from the base upwards. The raceme 

 may be either erect, as in Hyacintlius, Pyrola, or pendulous, as 

 in the currant and black cherry. 



299. The ament, or catkin, is a spike whose flowers are cov- 

 ered each with a scaly bract, instead of a calyx and corolla^ and 

 fall off together, all remaining still connected with the ra -his. 

 Ilx. Salix, Betula. 



300. The sPADiXiis a spike with a fleshy rachis enveloped in 

 a large bract, calle^pathe. Ex. Arum, Calla. 



301. Tlie CORYMB is the same as the raceme, having the 

 lower pedicels so lengthened as to elevate all the flowe s to 

 nearly or quite the same level. Ex. wild thorn (Crataegus). 



302. An UMBEL, resembles the coiynib, but the pedicels are of 

 nearly equal length, and all arise from the same point in the 

 common peduncle. Ex. Asclepias, Araha hispida, onion. 



303. A HEAD or cAPiTULUM is Similar to an umbel, bu' the 

 flowers are sessile or nearly so upon the summit of the pedun- 

 cle. Ex. button-bush, clover, globe -amaranth (Gomphrena). 



a. But the more common kind of capitulum is that where the 

 summit of the peduncle {rachis) is dilated into a broad disk {re- 

 ceptacle) bearing the sessile flowers upon its surface. Tl.is is 

 the kind of inflorescence peculiar to the vast family of the 

 Composite, and is equivalent to the comfound fimoers o^ the 

 caiiier botanists. 



h. In the capitulum there is a general i-esemhlancc to the simple flower, the 



