369 



M. R. H. Gamboge, 1913. la Proc. Roy. Soc. N.S.W. xlvii, 45 (1913), the 

 author adopts names for three venation groups, viz., Transverse (or right-angled) 

 oblique (or diagonal) and parallel, and defines them as follows : — 



1. "In the transverse venation the lateral veins are straight, nearly parallel to each other, and close 

 together, while the intramarginal vein is close to the edge, and the midrib is thick." 



2. " In the oblique venation the lateral veins are further apart than in the last form, while the intra- 

 marginal vein is at some distance from the edge." 



3. " 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." 



Mr. Cambage (loc. cit.) applies the term " parallel " to the venation, which 

 includes E. coriacea and E. stellulata. This is following Bentham to some extent, but 

 I think the use of the term " longitudinal " as adopted by Mueller and Naudin is better, 

 especially as the term " transverse " itsually applies to the position of the lateral veins 

 to one another, and not with respect to the midrib. 



" Leaf Venation. — A study of the venation of a series of Eucalyptus leaves discloses the fact that the 

 lateral veins are arranged at all possible angles (my italics, J.H.M.) with the midrib between the limits of 

 about 10 to 80 degrees. Attention was first drawn to the botanical and chemical agreement of these venations 

 in a paper read before this Society by Messrs. Baker and Smith, in 1901. For convenience of reference, the 

 venation in its relation to the midrib may be divided into three classes, viz., transverse or right-angled, 

 oblique or diagonal, and parallel, although none of the veins form quite so much as a right-angle with the 

 midrib, nor are any strictly parallel therewith, and the oblique venation may be regarded as that where 

 the lateral veins have a range of about 25 to 65 degrees with the midrib . . . (already quoted). 



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 distribution 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. fesselaris, which occurs in the north-eastern portion of the Interior, is rather more oblique than trans- 

 verse, 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 is significant that they are absent from Tasmania, and almost so from 

 Victoria, three species, E. corymbose/,, botrijoii.es, and macidata, 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 

 occiur in South-eastern Australia, though several are found connecting round through north to west 

 Australia. 



Judging by its wide distribution, and considering that this type of venation is practically identical 

 with that of the genus Angophora, and avoids the cold, the assumption seems warranted that it belongs to 

 the earliest form of Eucalyptus leaf, and also was developed in a warm climate in Northern 

 Australia.* 



* " The Tertiary Flora of Australia," by H. Deane, M.A., Proc. Linn. Soc. N.S.W. , xxv, 474 (1900). 



