ON SOME N.S.W. TAN- SUBSTANCES. 251 



me in the present series of experiments. Nevertheless, as the 

 improved process of Lowenthal is rapidly superseding all others 

 (at least on the continent of Europe), I will probably use it 

 •exclusively in future, in any future experiments I may be 

 permitted to bring under the notice of our Society. 



2. I began by treating the leaves with benzene in an exhauster, 

 similar in principle to that described by J. West-Knights (Analyst 

 viii., 65), but comparative experiments between fresh leaves, and 

 leaves thus treated, showed me that the oil present did not 

 perceptibly affect the determinations of tannic acid by the process 

 adopted. 



3. There is likely to be greater differences between analyses of 

 leaves than of barks, inasmuch as the life of a leaf is much less 

 than the bark of a tree, and so all the stages from the state in which 

 it consists almost entirely of cellular matter to that in which it 

 ■contains its maximum of fibre, and (usually) minimum of active 

 principles, are passed through in a comparatively short space of 

 time. 



4. The amount of tannin in some of the determinations may 

 appear high, but it must be borne in mind that the moisture in 

 leaves is comparatively great, and that these determinations have, 

 as usual, been calculated on the leaves thoroughly dried at 100° C. 



5. A convenient way of preparing the leaves for experiment is 

 to put them on a board and cut them in small portions by pressing 

 the sharp blade of a tomahawk over them. The fragments are 

 then passed through a small mill. 



6. The leaves and petioles only have been taken in each case, 

 all other portions of the twigs having been removed. 



7. The state of the leaves has been noted. Owing to the 

 dampness of the weather, in some instances, the collector was not 

 always successful in drying them in a satisfactory manner. 



8. The measurements of the leaves have been determined in 

 the following way. Twenty average leaves of each species have 

 each been measured with a millimetre rule, the greatest length 

 (including petiole), and breadth taken, and the mean calculated. 

 Mr. G-. S. Home, my assistant, has been kind enough to do this 

 for me. 



9. In each case I have attached a physical description of the 

 leaf, the minute description of the Eucalypts being from the 

 " Eucalyptographia" of Baron Mueller, while the less detailed 

 descriptions of Eucalyptus and Acacia are from the " Flora 

 Australiensis." In the " Eucalyptographia " the Baron takes 

 cognizance of the (a) shape, (b) colour, (c) lateral veins, (d) 

 circumferential vein — (the intermarginal vein of Bentham), (e) 

 oil dots ; and although these characteristics are of course not 

 sufficient for a diagnosis of a species, yet they are valuable aids 



