166 On the Compostfce. 



Bider that a true Bract ia the leaf from whose axil the flower bud 

 proceeds." Now as an Involucrum encloses an abbreviated spike, 

 and not a single flower bud, its parts cannot be Bracts, which alone 

 exist in the CompositaB in the form of the colourless, diminutive 

 chaff-like scales (palese), situated on the receptacle, and on the 

 exterior side of each individual floret. 



The student may satisfy himself of the correctness of these views 

 concerning the structure of the Compositae, — first by sketching a 

 typical plant, and then projecting the parts upon a common plane, 

 where they will be necessarily arranged as above described,or second- 

 ly by ascertaining theoretically what would be the effect if by lux- 

 uriance of growth the receptacle of a compound flower became 

 extended into an elongated axis. The scales of the involucrum 

 would then be separated and become spiral in their arrangement 

 the florets also would be disposed in a similar manner, and each 

 would be attended by its own proper bract, i. e. the chaff scale or 

 palea, and lastly the pappus would then be seen more plainly to be 

 the true calyx, crowning the real pericarp or seed vessel. More- 

 over it will be observed, that the order of flowering in a compound 

 flower, and in a spike exactly correspond, proceeding from below 

 upwards, in the latter case, and from without upwards in the former 

 one. It being obvious that the exterior flowers of the capitulum, 

 correspond with the inferior ones of a spike. In corroboration of the 

 foregoing views, I would refer to the flowers of the Dipsaceae or 

 Teazel family, which will serve to elucidate many obscure points in 

 the structure of the composita^, and conclude by impressing on the 

 students attention, that in Natural History arbitrary distinctions are 

 valueless, structural resemblances alone affording a sure foundation Jor 

 systematic arrangement. 



