324 BRAVAIS'* IDEAS OF INFLORESCENCE. [BOOK i. 



part of them, have two distinct modes of evolution; the 

 centripetal and the centrifugal. 



3. The SPIKE is a centripetal inflorescence. (Plantago, 



Ribes, Leontodon, &c.). Any centripetal group what- 

 ever, such as a partial umbel, raceme, spike, capitulum, 

 provided the peduncles are destitute of lateral bracts. 



4. The COMPOUD SPIKE is centripetal, with two degrees of 



evolution ; thus it is composed of partial inflorescences 

 arranged centripetally, and these partial inflorescences 

 are spikes. (Male flowers of Pinus.) 



5. The CYME is a centrifugal inflorescence. (Hemerocallis 



flava, Tradescantia, Strelitzia, Lamium, Cornus, Syringa.) 

 A centrifugal group, whose peduncles grow out of each 

 other. 



6. The THYRSE is an inflorescence at first centripetal after- 



wards centrifrugal. (Tamus, Delphinium, Laburnum.) 

 A group of cymes disposed centripetally, as the flowers 

 are in the spike. 



7. The SARMENTIDIUM is an inflorescence of which the first 



evolution is centrifugal : its partial inflorescences may 

 belong to either of the four previous forms. (Cichorium 

 Intybus, Yitis, Geranium molle, Asclepias). A group 

 of cymes or spikes arranged centrifugally, as the flowers 

 are in the cyme. 



8. The cyme of Monocotyledons appears to be typically 



uninodal* ; it is helicoid-\ t .or scorpioid ,% according as 

 its peduncles are homodromal , or antidromal. \\ It 

 may be binodal*, trinodal*, multinodal*, in its first 

 ramifications ; but it has a tendency to become uninodal 

 in its ultimate ramifications. 



9. The cyme of Dicotyledons is binodal, or multinodal ; the 



second is sometimes a simple variety of the first. In the 



* According as the peduncles bear 1, 2, or a variable number of nodes. 



f Where the flowers are arranged in succession in a spiral around a pseudo- 

 thallus (or axis of uniparous, that is one-peduncled, cymes, or sarmentidia, 

 formed by a series of successive peduncles, fitted into each other in such a way 

 that they seem to form but one and the same stalk, as in Hemerocallis fulva). 



Where the flowers are arranged in two rows parallel to the axis of the 

 pseudothallus, as in Canna indica. 



Where the direction of a spire is the same as on the central stem. 



|| Where the direction of a spire is the reverse of that on the central stem. 



