k 



M.WICHURA ON THE WINDING OF LEAVES. 305 



§ 125. 



Papilionaceae. — Dillwynia ericifolia, Sm.; D, glaberrima, Sm. ; 

 D, parvifolia, R. Br. ; Z). rudis, Sbr. ; D, laxiflora, Benth. ; 

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

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

 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. tribuloideSf 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-up style right. The twisted styles 

 of some species of Lathyrus, e. g. L, roiundifolius, Willd., and of 

 Phaseolus, 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 Kkewise acquiring an hehacal 

 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, 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 



* Sec 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 

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

 fining it. 



SCIEN. MEM.— iV«/. HisL Vol. I. Part IV. 20 



