Australian Flowering Plants. 183 



were not xerophytes, nevertheless the fact seems incontrovertible 

 that they are xerophytic as genera, and that the actual genera 

 were developed as xerophytic adaptations, and that in almost 

 all instances the genera, during their existence as these par- 

 ticular genera, never had an earlier mesophytic existence. 



This is strongly opposed to the idea that such genera were 

 part and parcel of the luxuriant growths of the mild and moist 

 Cretaceous in Europe and America. 



Third. — These types are almost entirely confined to the 

 hungry, sandy soils of Australia, exceptions being some of the 

 more recent species of Eucalyptus, and acacias. Soil condi- 

 tions such as these could scarcely be matched in Europe. 



Fourth. — The morphology and earlier history of the genera 

 considered are against the idea of matching leaf remains of 

 the mild and moist Cretaceous and Eocene in the Northern 

 Hemisphere, with modern Australian genera. Thus certain 

 lanceolate leaves, in the Northern Hemisphere, possessing a 

 venation not much akin to any recent Eucalypt have been 

 referred to the genus Eucalyptus, whereas all the botanical 

 evidence 4 indicates that this particular form of leaf lanceolate 

 more or less falcate and with twisted petiole, is only a recent 

 development and that the earlier form of leaf was more like 

 many Myrtese, being opposite, penniveined, generally sessile, and 

 more or less orbicular in shape. The venation also is peculiar, 

 and the earlier types had closely-set secondary veins, arranged 

 to the midrib at an angle approaching the right-angle. 



Grevillea, besides being a vigorous and hardy xerophyte, has 

 a very irregular perianth, and a follicular fruit. It is mainly 

 a shrub or undershrub, a dwarfed individual, a very spe- 

 cialized type, far removed from the primary type of the Pro- 

 teacese as generally conceived, which should have had a regular 

 perianth and should have had a luxuriant arborescent form. 

 Two of the species, however, are large trees, namely G. roousta 

 and B. striata. The same remarks apply to the cases of Hakea, 

 Banksia, and Dryandra. Persoonia, by some botanists, with 

 its regular perianth, and its drupaceous fruit, might be con- 

 sidered as a primary type, but its vigor, its xerophytism, and 

 its choice of the most hungry coarse sandy soils proclaim its 

 recency as a genus within the Australian States. Callistemon 

 is a highly specialized genus among the Myrtacece, closely 

 allied to Melaleuca (120 species approximately) and one which, 

 even to Australian botanists, would be difficult to describe from 



4 E. C. Andrews, Mvrtaceae, Proc. Linn. Soc. N". S. Wales, vol. xxviii, 

 p. 555, 1913. 



