BY HEXRY DEANE. 583 



have at least something in common, even if they are not made on 

 exactly the same plan; whereas those names refer only to the 

 common species with which we from our childhood have been 

 familiar. Even the genus Acer, most of the species of which 

 have leaves constructed on the palmate or tive-lobed pattern, 

 shows very considerable variation ; while the leaves of the 

 different species of the genus Quercus show innumerable varieties of 

 design, so great a divergence, indeed, that without following them 

 through all gradations and intermediate links it might be wondered 

 whether they could ever in the past have originated in one 

 ancesti*al stock. The leaves of the same species seem occasionally 

 to be made on a different pattern, as, for example, in Q. 

 agnatica, a North American species, where in some cases the 

 lateral or secondary veins run out to the margin of the lamina 

 and terminate in teeth, while in other varieties they do not reach 

 the margin at all, which is entire, but become lost in the general 

 reticulation. Q. cinerea is another example. 



The genus Quercus furnishes an excellent example of leaf- 

 variation, and I have taken the opportunity of offering a number 

 of examples for illustration. The genus is one which at the 

 present day is widely distributed and which is, according to 

 Ettingshausen, responsible for a great many of the fossil forms 

 found in the Miocene beds of Australia. It, therefore, possesses 

 a special interest. The number of species known to the authors 

 of the " Genera Plantarum " and recognised by them is 300. In 

 Plate xxxv. a sufficient number are figured to prove the greatvariety 

 of types. As before mentioned, Q. aquatica and Q. cinerea show 

 great varieties within the species. Preference may be made to 

 Ettingshausen's* Beitrage zur Tertiarflora von Java, where 

 remarkable variations of these two species are figured. 



I have tabulated below the variations shown in Plate xxxv., 

 grouping the leaves first, according to their shape ; secondly, 

 according to the character of the secondary veins; thirdly, according 

 to the tertiary system. The texture of the leaf, whether mem- 



* Sitzungsberieht der K. Akad. der Wissensch. 1 Abth. 18S3, Vol. 87. 



