8 DISPLACEMENTS, ETC. [CH. 



species of Equisetum, Casuarina, Hippuris and others, the 

 whorls have numerous leaves. 



The reader may compare the above with the state- 

 ments concerning the arrangement of buds in Vol. I. 

 Chap. IV. 



It must be observed that phyllotaxy is only a particular 

 case of the arrangement of lateral members, and that we 

 have to regard it as subject to more general laws than 

 need be referred to here. It has already been mentioned 

 that the phyllotaxy may differ in different parts of the 

 same plant, and even on the same branch ; examples occur 

 in Fritillaria imperialis, Oaks, Chestnuts, and several 

 species of Aloe and Monster a, where the angle of diver- 

 gence of the spirally arranged leaves changes as we pass 

 up the stem; and it is by no means uncommon to find 

 opposite leaves on the same branch with alternate ones, 

 e.g. Symphoricarpos, Salix purpurea, Rhamnus, Atriplex, 

 and occasionally the Ash and some others. 



Still more difficult cases are those where the real 

 phyllotaxy is obscured by crowding and displacements of 

 various kinds, or by the interposition of organs which are 

 not true leaves though they look like them. Examples of 

 the first kind are the fascicled leaves on the dwarf shoots 

 of many conifers, e.g. the Larch and Cedars, and on Ber- 

 beris vulgaris] the displaced leaves of many Solanacese, 

 such as the Bittersweet ; the false whorls of some Lilies, 

 &c, usually attributed to the suppression i.e. the non- 

 development of one or more internodes. Examples of 

 the second kind occur in the Bed-straws where stipules 

 assume the aspect of leaves, and have no buds in their 

 axils. 



These cases have also to be distinguished from others 

 where displacements are brought about by subsequent 

 twistings or torsions of the stem. Such torsions are very 



