THE GENTS EUCALYPTUS. 215 



the structure of the bark, and of paying due attention to the 

 configuration and valves of the seed vessels in determining indi- 

 vidual species. This system is exceedingly simple and natural, 

 and one that commends itself to the practical man as well as to 

 the botanist, but still it is not without its defects, for some species 

 are found to be half-barked in their youth, and perfectly smooth 

 when advancing in age, whilst others again, apparently of the 

 same standing, are seen growing near each other in both states. 

 Some species of white gum, and hybrid box, are instances of this 

 kind, but, nevertheless, as the great majority of these trees are 

 sufficiently similar in character to be recognized by the attentive 

 observer, I am inclined to regard Dr. Mueller's system of group- 

 ing the best that has yet been devised. Its advantages are clearly 

 seen in some of the groups, especially those of the iron barks, 

 the stringy barks, the bloodwoods, and the half-barked blackbuts 

 and box. Taking these well-known trees as types, it is not diffi- 

 cult to associate others with them, as they come under observation. 

 One of the principal difficulties to what may be termed the 

 popular study of the genus, arises from the different names which 

 are given to the same species in different districts. For instance 

 the blue gum of one colony is the red gum of another ; the 

 woollybut of one district is the peppermint of an adjoining one ; 

 whilst in one locality perhaps the same species may be indifferently 

 called grey gum, leather jacket, hickory, and hybrid box. With 

 regard to the groups previously enumerated, there is much greater 

 uniformity, for stringy bark, bloodwood, &c., retain the same 

 names wherever they occur. In a previous paper, I have already 

 alluded to Dr. Mueller's cortical system, but to set the matter 

 clearly before my readers, I shall give in his own words what he 

 modestly called an attempt to arrange the Eucalypti of tropical 

 and subtropical Australia, according to the structure, texture, 

 and shedding of their barks, accommodated to the use of the 

 colonists. He places all the species in six groups, in the following 

 order : (\.)Leiophloi(B, such as have the bark smooth on every side, 

 after the shedding of the outer layer, including the trees com- 

 monly called flooded gum-trees, white gum teees, blue gum-trees 

 in part, red gum trees in part, and yarrah trees. (2.) HemipJiloiae, 

 such as have the bark in the lower part of the trunk, persistent, 

 wrinkled, and full of clefts, in the upper part and in the branches 



