56 



THE TRANSVERSE SECTIONS OF PETIOLES OF EUCALYPTS 



Summarising the principal differences between them, as given in the " EuCalypto- 

 graphia," and in the more recent " Key to the System of Victorian Plants," as well 

 as those deduced from the transverse section of the petiole, they are as follows : — 



Such small differences completely justify tereticornis being regarded as merely 

 a variety of rostrata, but the latter, being the most cosmopolitan of all the Eucalypts 

 as far as Australia is concerned, might be expected to have undergone some 

 modification of structure in order to adapt it to its wider environment. 



3. E. viminalis is said to be closely allied to E. stuartiana as well as to E. 

 rostrata (Dec. 10). The thicker epidermis of E. rostrata, the generally smaller 

 cortical cavities, the feebly developed hard bast, and the relatively larger vessels 

 distinguish it. Stuartiana agrees, on the other hand, generally in the thinness of 

 the epidermis, the development of the hard bast, and the small size of the vessels, 

 but the cortical cavities are much smaller. 



4. When stuartiana and gunnii are compared, the differences are clearly 

 marked. In gunnii the thicker epidermis, the larger cortical cavities, and the wider 

 vessels form a contrast, but in the development of the hard bast, and the thickness 

 and curving of the wood, there is general agreement. 



6. Fie i folia and calophylla are nearly allied, and it is said of the latter that it is 

 " the only species to which E.ficifolia bears very close alliance " (Dec. 7). 



The sections reveal a very close general agreement indeed, the presence of two 

 internal canals normally in each, showing this. Calophylla has a much thicker wood- 

 pattern, and large and numerous cortical cavities, while in ficifolia they are very few 

 and very small, but the greater size of the former tree, as compared with the latter, 

 might account for this difference. 



6. Maculata and citriodora may be considered here, since both possess the 

 internal canals. It is stated that " citriodora can only be considered a variety of 

 maculata, differing merely in the exquisite lemon-scent of its leaves " (Dec. 3). And 



