362 PHYSIOGNOMY OF PLANTS. 



organs determine the peculiar character of the effects produced, the 

 outlines of light and shade. " Phyllodias," says Kunth, " can, 

 according to my view, only occur in families which have compound 

 pinnated leaves ; and in point of fact they have as yet only been 

 found in Leguminosae (in Acacias). In Eucalyptus, Metrosideros, 

 and Melaleuca, the leaves are simple (sirnplicia), and their edgewise 

 position arises from a half turn or twist of the leaf-stalk (petiolus) ; 

 it should be remarked at the same time that the two surfaces of the 

 leaves are similar." In the comparatively shadeless forests of New 

 Holland, the optical effects here alluded to are the more frequent, as 

 two groups of Myrtaceae and Leguminosa3 > species of Eucalyptus 

 and of Acacia, constitute almost the half of all tho grayish-green 

 trees of which those forests consist. In addition to this, in Mela- 

 leuca there are formed between the layers of the inner bark easily 

 detached portions of epidermis which press outwards, and by their 

 whiteness remind the European of our birch bark. 



The distribution of Myrtaceae is very different in the two conti- 

 nents. In the New Continent, and especially in its western portion, 

 it scarcely extends beyond the 26th parallel of north latitude, ac- 

 cording to Joseph Hooker (Flora Antarctica, p. 12); while, in the 

 Southern Hemisphere, according to Claude Gay, there are in Chili 

 10 species of Myrtus and 22 species of Eugenia, which, intermixed 

 with Proteaceae (Embothrium and Lomatia), and with Fagus obliqua, 

 form forests. The Myrtacese become more abundant beyond 38 S. 

 lat,. in the Island of Chiloe, where a Metrosideros-like species of 

 Myrtus (Myrtus stipularis) forms almost impenetrable thickets under 

 the name, of Tepuales; in Patagonia; and in Fuegia, to its extremity 

 in 56s S. lat. . In the Old Continent, they prevail in Europe as 

 far as the 46th parallel of north latitude : in Australia, Tasmania, 

 New Zealand, and the Auckland Islands, they advance to 50 5 

 south latitude. 



( 32 ) p. 244." Mdastomaceae." 



This group comprises the genera Melastoina (Fothergilla and To- 

 coca Aubl.) and Rhexia (Meriana and Osbeckia), of which we found, 

 on either side of the Equator in tropical America alone, 60 new spe- 

 cies. Bonpland has published a superb work on Mclastomacese, in 



