104 INFLORESCENCE. 
cences, are centripetal, while the general inflorescence is centri- 
fugal, that is, the central head is developed before the lateral 
ones. But in the Labiate the partial inflorescences (verticilas- 
ters, 309) are centrifugal, while the general inflorescence is — 
centripetal. 
296. Of centripetal inflorescence the principal varieties are, 
the spike, raceme, ament, spadix, corymb, umbel, head, 
panicle, and thyrse. 
297. The spike is an inflorescence consisting of several ses- 
sile flowers arranged along a common peduncle (rachis). Ex. 
Plantago, Verbascum. 
» 298. The raceme 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 evect, as in Hyacinthus, Pyrola, or pendulous, as 
in the currant and black cherry. 
299. The ameEnr, or catkin, is a spike whidsis flowers are cCov- 
ered each with a scaly bract, instead of a calyx and corolla, and 
fall off together, all remaining still connected with the rachis. 
Ex. Salix, Betula. 
300. The spaprx is a spike with a fleshy rachis enveloped in 
a large bract, called spathe. Ex. Arum, Calla. : 
301. The coryme is the same as the raceme, having the 
lower pedicels so lengthened as to elevate all the flowers to 
nearly or quite the same level. Ex. wild thorn ( Crategus). 
302. An umBEL resembles the corymb, but the pedicels are of 
nearly equal length, and all arise from the same point in the 
common peduncle. Ex. Asclepias, Aralia hispida, onion. 
303. A HEAD or CapituLuMm is similar to an umbel, but the 
flowers are sessile or neatly so upon the summit of the pedun- 
cle. Ex. button-bush, clover, globe-amaranth (Gomphrena). 
a. But the more common kind of capitulwm is that where the 
summit of the peduncle (rachis) is dilated into a broad disk (re- 
ceptacle) bearing the sessile flowers upon its surface. This is 
the kind of inflorescence peculiar to the vast family of the 
Composite, and is equivalent to the compound flowers of the 
earlier botanists. 
b. In the capitulum there is a general resemblance to the simple flower, the 
og th ie i i bet, ei i ae ia 
