AS AIDS IN THE DETERMINATION OF SPECIES. 57 



it is a striking corroboration of this that a study of the two sections leads to the 

 same conchision. Further, there is a remarkable resemblance between the relations of 

 the sections of maculata and citriodora, and calophylla and ficifolia. There is the 

 similar stout and slender wood-pattern respectively in both, although the cortical 

 cavities are about equally numerous and equally large in maculata and citriodora. In 

 ficifolia it would appear that the stimted habit of the tree had rendered large and 

 numerous cortical cavities less necessary, and so they have dwindled down in size and 

 numbers, whereas the variety of maculata has lost nothing of its stateliness. Such 

 are some of the affinities which have been noted by Baron von Mueller, and which 

 are borne out as well by the transverse sections of petioles. Let us turn now to some 

 others which do not agree with our sections. 



The affinities of E. viminalis have already been discussed. 



7. E. lehmanni is said to be "specifically inseparable from E. corniita" (Dec. 

 9), but a glance at the two sections would not suggest it. There is resemblance in 

 the large and numerous cortical cavities, and in the much broken wood-pattern, but the 

 vessels in cornuta are much larger and more numerous, and the wood-curve is consider- 

 ably thicker. Altogether, the resemblances in the sections would not justify their being 

 classed together as the same species, or the one as a variety of the other. 



How are we to regard a discrepancy of this sort ? Are we to regard the deep- 

 seated characters of the leaf-stalk as delusive ? External resemblances and allied 

 internal anatomy do not always go together, for there may be fundamental difference, 

 accompanied by superficial resemblance, just as there maybe fundamental resemblance 

 with superficial difference. We consider that the relationship may still hold between 

 E. cornuta and E. lehmanni, the latter being a variety of the former, even in spite of 

 seeming contradiction from the section, when it is remembered what aberrant and 

 extreme forms are assumed by some species, and the extent of their variability. 

 That this applies here will now be shown. In arranging our sections mdependently of 

 external characters in the first instance, E. occidentalis was placed next to E. 

 lehmanni, which naturally formed the last term of the present series. The section 

 of the petiole of E. occidentalis exhibits a wood-pattern of such an irregular natm-e 

 that it is difficult to say what it resembles exactly, and yet it is suggestive of 

 resemblance to a number of forms. It is, in short, just such a form of section as 

 might easily develop into several of the others, and so we were unable to correlate it 

 with any. In considering the affinities of E. occidentalis in the " Eucalyptographia " 

 (Dec. 6), much light is thrown on the present difficulty. 



First of all, we are informed that E. cornuta, E. obcordata, and E. occidentalis 

 " seem to be the only three entitled to specific rank m the series of cornuta or 

 orthostemoneae, and even the lines of demarcation between these three are not always 



