280 M. WICHURA ON THE WINDING OF LEAVES. 



liaceae ; and the petals of Chrystea speciosa, Ward et Hartw., 

 Strophanthus divergens, Graham — Fam. of Apocynaceae ; Cycla- 

 men eurojxBwrii L.^ Lysimachia punctata, Wallr. — Fain, of Pri- 

 mulaceae ; — are all wound to the left in the bud, and to the right 

 when the flower blows. The awns oi Arrhenatherum elatum, 

 M. & K., at first wind slightly to the left below the angle ; sub- 

 sequently, as the seed is maturing, to the right in the same situa- 

 tion. It is probable that similar phaenomena will be shown to 

 occur in very many Grasses with winding awns. The appendages 

 of the seed (beak of the carpel?) of Erodium cicutarium, L^Herit., 

 are wound to the left round the carpophore; after separating 

 from it they wind to the right. See PI. IX. fig. 4. nos. 1 & 2. 



§43. 



2. Differentiation of the Leaf in reference to Point and Base, 



Alstroemeria pelegrina — Fam. of Amaryllidaceae : — stem- 

 leaves winding to the right at the apex and to the left near the 

 petiole. Avena sativa, L., and the allied species Fhalaris minor, 

 Li., &c., Lagurus ovatus, L. — Fam. of Gramineae, — and Xerotes 

 purpurea,^r\di\. — Fam. of Juncaceae : — stem -leaves wound to the 

 left at the points and to the right near the bases. (See fig. 5.) 

 In like manner the awns of many grasses, especially of the 

 genera Avena, Stipa, Danthonia, Slc, in which the angle or 

 ' knee ' forms the boundary of the two oppositely-directed 

 windings, so that the curvature is to the left above the knee and 

 to the right below it. Chcotobromus Dregeanus, N. ab E., Ck. 

 stiictus, N. ab E. : the palea runs out into two teeth above, the 

 awn being fitted in between them ; the two teeth wind to the left, 

 the awn to the right below and to the left above. Strophanthus 

 dichotomus, D.C. — Fam. of Apocynaceae: — the left-wound flower- 

 buds are slightly rolled to the left at their points and twisted to 

 the right below. A second change of the direction occurs in 

 the awns of Macrochloa arenaria, Koch. Immediately below 

 the knee they wind to the right, then further down to the left, 

 and quite at the bottom again to the right. The very long style 

 of Protea grandijlora, Thunb., changes three times to opposite 

 sides, but here the place which the two directions occupy is not 

 determinate, as in the examples above mentioned, for apparently 



