AS AIDS IN THE DETERMINATION OP SPECIES. 21 



The accomjianying clrawiDgs almost render description unnecessary, but as this 

 is the main portion of the jjaper, the determining characters of each form examined 

 ■will be briefly given. 



Before doing so, however, it will be necessary to fix upon some definite arrange- 

 ment, and a geographical one may be followed, in order to see how far anatomical and 

 geographical relations agree. 



Table I. exhibits the thirty different forms investigated, variously arranged as far 

 as the data will permit. It is hardly needful to state that the necessary information 

 has been obtained from the " Eucalyptographia," and we have simply thrown it into 

 tabular form. The only exception is the arrangement according to cortical cavities, 

 central canals, and wood curve, which has been deduced from our own researches. 



Table II. starts with the forms arranged according to their geographical distri- 

 bution, and places opposite each the characters respectively deduced from the 

 transverse section of petiole, the leaves, stomates, fruit, anthers, pollen, and bark. 



The very different affinities shown by these various systems of arrangement 

 only emphasises the fact that it is not by solitary characteristics affinities are deter- 

 mined, but by the complex of characters, which go to the making up of an individual 

 whole. 



The transverse sections will likewise show that along with a certain amount of 

 variability there is sufficient constancy to give them a characteristic appearance for 

 the different species. The most striking features are : Size and shape of section, 

 relative thickness of epidermis, size and number of cortical cavities, frequency or 

 scarcity of crystals, density and continuity, or the reverse, of hard bast, pattern of 

 the wood, and size and distribution of the vessels. 



Since all these details are only necessary for complete description, the charac- 

 teristic features are given at the end as a sort of summary of characters, serving for 

 all practical purposes. 



As regards the central canals, they occur in only a few of the investigated 

 species, viz., E. calophylla, ficifolia, and maculata, with its variety citriodora. 



Two seems to be the normal number, but since each may divide in a forked 

 manner, the number is sometimes increased to four, or even six {maculata). (See 

 remarks in description of each species.) 



In stating the characteristic featm-es of the various sections, it is often found 

 necessary to speak of the relative sizes of different parts, such as the section of the 



