M. WICHURA ON THE WINDING OF LEAVES. 305 



125. 



Papilionacea. Dillwynia eritifolia, Sm.; D. glaberrima, Sm. ; 

 D. parvifolia, R. Br. ; D. rudis, Sbr. ; D. laxlflora, Benth. ; 

 D. pinea, Sbr. ; Ccelidium ciliare, Vogel ; Amphithalea, Eckl. et 

 Zeyh. : stem-leaves right. Trifolium circumdatum, Kze. ; Tr. 

 resupinatum, L. : the resupination of the flowers of these two 

 plants is produced by a half revolution of the tube of the co- 

 rolla toward the right. Similar windings of the tube of the 

 corolla are met with also in Trifolium fragiferum. But the 

 winding is much slighter here, inconstant in its direction, and 

 amounts scarcely to a quarter of the circumference. Medicago : 

 the legumes of most of the species wind to the left. The fol- 

 lowing have right-wound legumes : M. tuberculata, Willd. ; 

 M. tribuloides, Lam.; M. rigidula, Lam. ; M. striata. For Me- 

 dicago littoralis, Rohde, see 36*. Sesbania cegyptiaca, Pers. : 

 the very long linear articulated pod left. Crotalaria retusa, L. ; 

 Cr. verrucosa, L. ; Cr. ovalis, Pursh ; Cr. quinquefolia, L. ; Cr. 

 carinata, Steud. : the dried-tip style right. The twisted styles 

 of some species of Lathyrus, e. g. L. rotundifolius s Willd., and of 

 PhaseoluSy follow the same direction. The revolution, however, 

 begins here in the bud, and is imparted to the keel tightly en- 

 closing the style, the former thus likewise acquiring an heliacal 

 winding. Petalostemon candidum, MX. : drying-up style wound 

 in many flowers to the right, in others to the left. Dalea bra- 

 chyptera, Kunze : style slightly left. For the revolution of the 

 phyllodia in Acacia micracantha 9 Desf., Fam. of Mimosece, 

 see 45. 



XIV. Cause of the Curvature of Wound Leaves. 



126. 



The curvature of the winding leaf depends either on an un- 

 equal tension of its margin in relation to the axis, or on an in- 

 equality of length of its two surfaces. The specific gravity, 

 which otherwise is certainly to be enumerated among the causes 

 of the curvature of the leaf, comes but little or not at all into 



* See also A. Braun on "Regular Revolutions in the Vegetable Kingdom," 

 Flora, 1839, i. 313, in which the heliacal winding of the legumes of the species 

 of Medicago is described correctly according to DeCandolle's method of de- 

 fining it. 



SCIEN. MEM, Nat. Hist. VOL. I. PART IV. 20 



