The Similarities and Dissimilarities of Acacia decurrens, mollissima, and dealbata.

A. decurrens, A. mollissima, and A. dealbata are very closely allied botanically, and have, in fact, been considered by various botanists as varieties of the same species; for the most ardent advocate of splitting up species cannot produce any very marked differences between them.

I have summarized below the differences between the three which are held to be specific, from a botanist's point of view; and from the point of view of the technologist all that I can say is that the very bad name of A. dealbata with some people is not borne out by my experiments, all the samples used in which are true to name, the utmost precaution being adopted to ensure accuracy. From my experiments it would appear that the percentage of tannic acid in A. dealbata is nearly two-thirds of that contained in A. decurrens and A. mollissima, which two species have very close affinities. They are at once distinguished in the field from A. dealbata by the ashy or silvery hue of the latter; but the differences between the three are not very marked in dried specimens, and that is the reason, I presume, why they have not hitherto been comparatively figured. I have spent much time endeavouring to note differences which might be brought out in a figure, but know of none other than the degree of constriction between the seeds. Careful examination of the subjoined comparative table will show that there are no sharp lines of demarcation between the three species, and that those botanists who look upon A. mollissima and A. dealbata as varieties of A. decurrens take up a position which is apparently as strong as those who divide them into separate species. Reference to the tables will show that A. decurrens and A. mollissima are very closely allied as regards yield of tannic acid, and, from the point of view of the tanner, I do not think there is a pin to choose between them. The average percentage of tannic acid in A. dealbata is, hovever, consistently lower than in the other two species or

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varieties; but not so much lower as to cause its rejection as a wattle-bark without discrimination. I have already alluded to the subject under A. dealbata, but consider the matter of sufficient importance to repeat that A. dealbata is only rejected when the better barks A. mollissima or A. decurrens are readily available; for reference to the detailed accounts of several other barks shows that barks even inferior in quality to that of A. dealbata are in daily use by country tanners.

(1)   (2)   (3)  
Vic., N.S.W., Q.  S.A., T., Vic., N.S.W., Q.  Vic., N.S.W., Q. 
FOLIAGE, &c.:— 
......  “At first yellowish.”—F.v.M.  “At first whitish.”—F.v.M. 
“Leaves and branches bluish.”—Spicer. 
Pinnules conspicuously longer  ......  ...... 
Branchlets from decurrence of leaf-stalks more angular than (2) or (3).  ......  ...... 
Branches almost glabrous  “Branches with yellow down.”—Spicer.  The tips of the twigs are sometimes also yellowish.—J.H.M. 
Second.  Third.  First. 
......  “Late in Spring or beginning of Summer.”—F.v.M.  “Early in Spring.”—F.v.M. 
Although I know the flowers of A. decurrens very well, I should be sorry to dogmatise as to the tint of yellow.—J.H.M.  “Usually pale yellow.”—F.v.M.  “Usually bright yellow.”—F.v.M. 
Rather narrow; much constricted between the seeds; strongly compressed.  Rather narrow; constricted between the seeds.  Rather broadish; hardly constricted between the seeds. 
Shorter than (3); arillar appendage shorter.  Arillar appendage pale; much attenuated. 
“Ripens seeds in 14 months.”—F.v.M.  “Ripens seeds in 5 months.”—F.v.M. 
“Not quite so powerful as (2).”—Mueller. (As regards tannic acid).  Not a pin to choose between (1) and (2) as regards the bark.—J.H.M.  “Much thinner bark, and greatly inferior to (1) and (2).”—Mueller.