natural Family of Plants called Composites. 
119 
in Composite, especially in the tribe of Helianthece , to which 
Melananthera belongs. 
In M. Cassini’s Memoir on the Stamina of Composite the retrac¬ 
tion of antherae 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, namely Helianthece; whose filaments below 
the joint, he says, wither very soon after foecundation*. To this 
withering, which he does not mention as occurring in any other 
tribe, the phenomenon 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 state of 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 Composite 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 Cinarocephalce; 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 lxxviii. p. 278. 
f Ephemerid. Acad. Nat. Curios, cent. ix. et x. p. 194. 
J Discorso della Irritabilita d’alcuni Fiori. Firenze 1764. 
§ Von Einigen das Geschlecht der Planzen betreffenden versuchen.3. fortsez. p. 125. 
irritability 
