ANNOTATIONS AND ADDITIONS. 199 



Botanique, p. 106, 120, and 700; Darwin, Journal of 

 Researches, 1845, p. 433). Morphological laws in the 

 development of the leafy organs determine the peculiar cha- 

 racter of the effects produced, the outlines of light and 

 shade. " Phyllodia," 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 Leguminosse, (in Acacias) . In Eucalyptus, Me- 

 trosideros, and Melaleuca, the leaves are simple (simplicia), 

 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 Myrtacea3 andLeguminosa3, species of Eucalyptus 

 and of Acacia, constitute almost the half of all the greyish 

 green trees of which those forests consist. In addition to 

 this, in Melaleuca 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 Myrtacese is very different in the 

 two continents. In the New Continent, and especially in 

 its western portion, it scarcely extends beyond the 26th 

 parallel of north latitude, according 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 



