586 THE TERTIARY FLORA OP AUSTRALIA, 



pick out any one variety and say that is the Eucalyptus type. 

 The secondary veins afford a great many different varieties. 

 Observe for instance : — 



E. coriacea and E. stellulata with their longitudinal veins; E. 

 Siberiana and others with secondary veins placed at an acute 

 angle with the midrib. 



Follow the series down till the secondary veins become almost 

 transverse. 



E. microcorys, unlike most Eucalypts, has quite thin leaves. 



The shape of the leaves might be thought to be fairly uniform 

 and that they would all fall under the description of linear, lanceo- 

 late, acuminate, more or less falcate, and oblique at the base. 

 All these characters break down in some of the specimens. Then 

 it has been supposed that the intramarginal vein would be a 

 pretty sure guide. It is, however, found in Myrtacece generally, 

 in some Proteacece, in many Apocynacece, in many species of Ficus, 

 and in genera belonging to many other natural orders. It is 

 further to be remarked that in Eucalyptus itself its position is 

 very variable, so that while in some leaves it is a considerable 

 distance from the margin, in others it is so close to the edge as 

 to be barely distinguishable. 



In Plate xxxvii. are shown various Australian representatives 

 of the Natural Order Laurinece. It will be seen that the 

 Cinnamomum character is not confined to the genus C innamomum, 

 and that the Laurus type of venation is exemplified in some of 

 these Australian genera. The Cinnamomum type makes its 

 appearance also in Rhodamnia (My rtacea?), Mallotus ( Euphorbiaceaj ) 

 both figured in the plate. It is clear that if either of these wei*e 

 found in the fossil state, and especially if they were fragments 

 only, they might easily be taken for Cinnamomum. The same 

 remarks apply with equal force to certain leaf-forms of the 

 genera Smilax and Rhipogonum (Liliacece) and to Rhodomyrtus 

 ( Myrtaceai). 



The similarity in structure between certain leaves of the Order 

 Proteacece and others of the Order Sapindacece is very marked. 



