164 THE INSTABILITY OF LEAF-MORPHOLOGY, 



who writes, "The case of E. coriacea is a notable instance of the 

 decreasing size, increased succulence, and glaucousness of the 

 leaves, as the higher elevations ai'e reached." Mr. Maiden also 

 writes at some length on the question of the specific rank of E. 

 pulverulenta Sims, on the validity of which species some doubt 

 had been expressed by previous writers, chiefly in respect of the 

 variabiHty of leaf -characters (These Proceedings, 1901, p. 547). 

 In (20a), Mr. J. H. Maiden, referring to " A species in the 

 making," — akin to K. vielaiiophloia F.v.M.,(p.233), says: — "We 

 have been of course aware for many years how variable is the 

 foliage of E. melauophloia, lanceolate-leaved forms being well 



known. Particulars may be found in (18; Part 12, p.71) 



Owing to changes of environment, it is very often the case that 

 we have breaks, and in the present case we may have a break 

 from E melauophloia in the direction of narrower, more petio- 

 late leaves, with other minor differences." In (20b), Mr. Maiden, 

 under E. Risdoni Hook. f.,(p.28) says : — " Perusal of p. 175, and 

 of Plate 32 of my work (18) vvill show that I had already con- 

 firmed Bentham's observation by noting 'lanceolate leaves are 

 common on the tops of branches of E. /^isdoid,' and Mr. Deane 

 and T compared them with a similar phenomenon in E. pidvern- 

 lenta (cinerea).' In a paper (20d, MS.), (extracts from which I 

 have, by the courtesy of the author, been permitted to quote) 

 Mr. Maiden, under Homoplasy, writes : — " In Eucalyptus, so 

 often do organs (particularly leaves) simulate each other, that it 

 is usually necessary to demand specimens exhibiting a full suite 

 of organs, in order that species may be determined"'; and he gives 

 the following quotation from Daydon Jackson's "Life of Ben- 

 tham" (p.217), "On 27th April, 1870, Mr. Wilson Saunders 

 airaiii contributed to the Linnean Society, a set of mimetic 

 plants, as the President phrased it, "a very interesting exhibi- 

 tion of pairs of plants with almost identical foliage from very 

 different natural orders .... very much alike when in leaf only, 

 so as in many cases to be quite indistinguishable, eighteen pairs 

 of them" (p. 220;. A further reference is given (loe. cit.) to 

 " Nature," iv., p. 11. In a Chapter on Provisional Species, the 

 author, when considering Mature Leaves (Eucalyptus) says : — 



