50 



THE TEANSVERSE SECTIONS OF PETIOLES OF EUCALYPTS 



VII. — Scheme for Determining Species. 



As our investigations proceeded it became evident that some scheme of arrange- 

 ment might be devised, whereby the different species could be more or less completely 

 separated, by taking all the characters derivable from the leaf. In framing this 

 scheme we took the external leaf-characters principally from Baron von Mueller's 

 " Eucalyptographia," where the most minute peculiarities are clearly noted, and 

 combined them with such characters as were peculiar to the section of the leaf- 

 stalk. 



It will be understood that this scheme is by no means meant to be final, since it 

 is concerned with thirty species selected at random from the whole range of genera ; 

 but it is merely given to show how such a scheme might be constructed for any definite 

 and restricted section of the Eucalyptus-species. Thus, when all the Victorian species 

 have been investigated as to the structure of their petioles, it will be possible so to 

 arrange them that the different species will be more or less clearly marked out. 



With this qualification, the scheme applicable to the thirty species will now be 

 indicated, and may be generally represented as follows : — 



Section I. — Central Canals present. 

 „ II.— „ „ absent. 



Section I. 



A. Cortical Cavities large — 



1. Hard Bast well developed — 



2. Hard Bast feebly developed — 



B. Cortical Cavities small — 



1. E. maculata. 



2. E. maculata, var. citriodora. 



3. E. calophylla. 



4. E. ficifolia. 



Section II. 



A. Leaves equally green on both sides — 

 1. Cortical Cavities large — 



a. Hard Bast well-developed- 



