natural Family of Plants culled Composite. 119 



in Compositae, especially in the tribe of Helianthece, to which 

 Melananthera belongs. 



In M. Cassini's Memoir on the Stamina of Compositae the retrac- 

 tion of antheree is not expressly noticed. This appearance, how- 

 ever, can hardly have escaped so accurate an observer; and his 

 opinion respecting its cause may perhaps be inferred from an 

 observation he has made on the stamina of the tribe in which it 

 is most remarkable, nauiely HelianlhecB; whose filaments below 

 the joint, he says, wither very soon after foecundalion*. To this 

 withering, which he does not mention as occurring in any other 

 tribe, the phaenomenon in question may be supposed to be 

 ascribed. 



But it appears to me, that the contraction or collapse of the fila- 

 ments, from their previous stateof extension, is a vital action, and 

 not the effect of withering or decay, which, however, speedily 

 follows it. For the contraction may in great part be prevented 

 by the separation of the floret, when the filaments are in the state 

 of extension : and in many genera of Compositae the antherae 

 are never retracted, but continue to project till they fall off 

 with the corolla. 



This contraction is also analogous to the more evident motion 

 or irritability of the filaments long ago noticed by Borelli and 

 Alexander Camerarius-f- in certain Cinarocephalcz ; and more 

 fully described in the same tribe by Dal CovoloJ; whose 

 observations are confirmed and extended to other subdivi- 

 sions of Compositae by Koelreuter §. A similar contraction and 



* Journal de Physique, tome Ixxviii. p. 27S. 



t Ephemerid. Acad. Nat. Curios, cent. ix. et x. p. 194. 



X Discorso della Irritabilita d'alcuni Fiori. Firenze 1764. 



§ Von Einigen das Geschlecht der Planzen betreffenden versuchen.3. fortsez. p. 125. 



irritability 



