172 THE INSTABILITY OF LEAP-MORPHOLOGY, 



Of heterophylly within a species, and homoplasy in opposing 

 species, and the gradual metamorphosis of the leaves of one species 

 into those of another, this well named Order provides numerous 

 examples. Members present at the Meeting of this Society in 

 July, 1910, will recollect the remarkable series of examples 

 illustrating interchangeable leaf-characters between three Gre- 

 villeas, viz., G. Gaudichaudii R.Br., G acanthifolia A. Cunn., and 

 G lauri/olia Sieb., exhibited by Mr. J. J. Fletcher, which he 

 presented as evidence of reciprocal hybridism within these species 

 (These Proceedings, 1910, p.433). The leaves of Grevillea 

 linearh R.Br., and those of G. sericea R.Br., overlap, and, in 

 .some of the narrower forms, are not easily separated; the foliar 

 characters dividing G. sphacelata R.Br., and G. phylicoides R.Br., 

 are not strong. In all four of these Grevilleas, the tomentum — 

 one of the characters relied on by Bentham (4; v., p. 464) to 

 separate the two latter -is subject to considerable interchange- 

 able variation, both in colour (silvery to ferrugineous), and 

 tiocculence, as opposed to appression. A series of examples of 

 G. oleoides Sieb., are here noted, showing variation from narrow- 

 linear, with revolute margins, to broad lanceolate, the margins 

 but slightly recurved, and ranging from 3 x /g to 3 x f inch 

 (Heathcote; October, 1915; A. A. Hamilton). 



Spencer Moore (21; p.259) says, "some Proteacea;, Grevilleas 

 and Ilakeas especially, can scarcely be distinguished from Acacias 

 when not in Hower or fruit.'' The terete-leaved Hakeas, which 

 exhibit, within the limits of a species (13; 1915, p. 289, //. puyioni- 

 formis Cav.), as great a variation as is found in opposing species, 

 are gradually altered via the dimorphic-leaved H. microcarpa 

 R.Br., into the flat-leaved section of which the variable H. 

 dactyloides {iZ; 1914, p. 88) is a representative. The leaf-varia- 

 tion in H. daclyloides has been noted by Mr. J. H. Maiden (19; 

 v., p.l47, PI. 179), and several forms of leaf are depicted in the 

 admirable plate by Miss M. Flockton, illustrating this species. 

 A xerophytic condition inducing similarity in the leaves of 

 certain members of a species, and causing variation between 

 them and their congeners of the same species, which are not 

 subjected to similar treatment, is exemplified in Isopogon atie- 



