58 THE TRANSVERSE SECTIONS OF PETIOLES OF EUCALYPTS 



very clear." So this brings E. occidentalis into some sort of affinity v^^ith E. cornuta, 

 and, by implication, with its variety, E. lehmanni. When the section of the latter is 

 compared with E. occidentalis, there is undoubtedly a certain resemblance, but not 

 directly, with E. cornuta. 



Agam, it is found from extended observation and increased material, that E. 

 occidentalis runs more or less into at least six named species (not reckoning two 

 varieties of E. cornuta), viz. : — 



E. spathulata. Hook. 

 E. macrandra, F. v. M. 

 E. cornuta, Labillardiere. 

 E. obcordata, Turcz. 

 E. redunca, Schauer. 

 E. pachypoda, F. v. M. 



And the inference is that E. occidentalis is capable of and subject to a vast 

 amount of variability. 



Nay, further, in the concluding sentence of the notice of this form, it is stated 

 " E. occidentalis, in its scope as here considered, seems so variable as to change much 

 of former ideas as regards the precincts of Eucalyptus-species, a similar playfulness 

 of forms having been observed by me in E. stricta and E. incrassata, the characters of 

 shrubby Eucalypts proving generally less constant than those of the tall timber-trees 

 of this genus" (Dec. 6). 



In such a sentence as that there is contained the essence of a volume on the 

 "Origin of Species." And when we consider that at least three sjiecies — E. glauca, 

 E. pulverulenta, and E. perfoliata — have been based upon the young state of E. 

 globulus (Dec. 6), it is not to be wondered at, but rather to be expected, that in such 

 a variable genus of plants there would be striking resemblance in internal structure, 

 as well as a certain amount of diversity. 



IX. — Concluding Eemarks. 



If transverse sections of the petioles can be used as an important aid in the 

 determination of species, then it is evident that this test may be applied where there 

 is doubt as to specific identity. 



