46 R. H. CAMBAGE. 



In the parallel venation the lateral veins are well apart 

 and sometimes show a system of looping, the intramarginal 

 vein being well removed from the edge, and the midrib is 

 thin. 



Seeing the very great divergence which often exists 

 between the seedling and adult leaves of the same tree, 

 and also in the venation of the adult foliage of many species, 

 it seems reasonable to suppose that the various ultimate 

 types of venation have been developed in response to some 

 influence or dominating condition, and if the distribution 

 of these various types can be shown, some data should 

 thereby be furnished that would assist in deciding what 

 that particular regulating influence may have been. 



Transverse venation, — Upon investigating the distribu- 

 tion of those Eucalypts which have the transverse venation, 

 it is found that they form a very small proportion of the 

 Eucalypts of South Eastern Australia, and are commonest 

 in the Coastal Area, next in the Interior, and on the Western 

 Slopes, and last in the Mountain Region, In the last named 

 division, Eucalypts having this class of venation appear to 

 be quite absent above an altitude of 3,000 feet, while one 

 species, E. trachyphloia, occurs on the northern part of the 

 Western Slopes, and another E. terminalis in the northern 

 portion of the Interior. The venation of E, tessellaris, 

 which occurs in the north-eastern portion of the Interior, 

 is rather more oblique than transverse, and shows a sort of 

 transit stage. It will be seen therefore that the Eucalypts 

 with the transverse venation avoid the cold parts, and it 

 js significant that they are absent from Tasmania, and 

 almost so from Victoria, three species, E. corymbosa n 

 botryoides and maculata occurring sparsely near the coast 

 in the extreme north-east corner of that State. Further, 

 there are only about a dozen species of this class which 

 occur in South Eastern Australia though several are found 

 connecting round through North to West Australia. 



