PRESIDENT'S ADDRESS. 



37 



while the two still lower pairs are more or less at right angles to the axis; (3) 

 that there is a terminal seta representing a remnant of the missing terminal 

 leaflet, unless it is accidentally wanting, as it often is in the full-grown leaves, 

 ■which is green and very conspicuous in quite young fresh leaves; 

 and (4) that the petiole, real or apparent, is somewhat variable in length in 

 different leaves, and may be about half as long again as the lowest internode, or 

 even a little more. 



In the pari-bipinnate leaves of the Australian Acacias, it will be noticed — {!) 

 that, in the absence of the terminal pinna, represented by the terminal seta, the 

 pinnfe of the apical pair invariably, as far as I have seen, move inwards so as 

 almost or actually to touch or even slightly overlap; that those of a few pairs 

 below, if the pairs are numerous, may also move inwards, but that some of the 

 lowest pairs may be more or less at right angles;— (2) that the internodes are 

 about as long as the spread of an opposite pair of expanded leaflets measured 

 from tip to tip, but may be slightly longer; the internodes of the same leaf may 

 also vary slightly in length— and (3) that the petioles, apparent or real, are 

 short if the leaflets are short, excessively short sometimes as in A. Bailey ana, and 

 A. Jonesii, but nnich longer, though still relatively short, if the leaflets are long 

 as in A. prulnosa, or very long indeed, as in A. elata. Following are the mea- 

 surements of the leaves of the five species available : — 



A. Baileyana — 4 pairs of pinnae; common petiole, IJ; lowest internode, i; 

 petiole, i inch. (PI. iv., fig. 1). The lai-gest number of pinnae noticed is five 

 pairs. The leaflets of this species are not sensitive. 



A. discolor — 9 pairs of pinnae; common petiole, 4J ; lowest internode, A; 

 petiole, 1 inch. In another leaf on the same branch, tlie petiole was no longer 

 than the internode above. 



A. decurrens — 17 pairs of pinna;; common petiole. 51; lowest internode, ^; 

 petiole, I inch. 



A. pruinosa — G pairs of pinnse; common petiole, Hi; leaflets up to 5; lowest 

 internode, J; petiole, If inch. 



A. elata — 5 pairs of pinnae; common petiole, 9f ; leaflets up to 1| (Bentham 

 gives up to 2 inches); lowest internode. If; petiole, 2| inches. Three other 

 leaves have the petioles somewhat shorter. This species has very long pinnas, 

 up to more than 8 inches. 



Bipinnate leaves may be short, or long, or of intermediate length, according 

 to the number of pairs of pinnae present; that is, according to the number and 

 length of the internodes, and the length of the apparent petiole. The number 

 of pairs of pinnae present in a given length depends on the length of the leaflets, 

 and this is a very variable quantitj'. 



The bipinnate leaves of A. elata and A. pniiiiosa, of all the twenty-two 

 species described in the Flora Australiensis, and as described therein, have the 

 longest leaflets. Therefore, they may be expected to have, as they actually have, 

 the longest internodes, and the longest petioles, real or apparent. No seedlings 

 of euphyllodineous Acacias have as yet, been described by Cambage, with leaflets 

 promising to be anytliing like as long as those of A. elata. 



Allowing about 3 inches as the maximum length of the petioles of the Aus- 

 tralian bipinnate Acacia with, by far, the longest leaflets known, what valid 

 ground is there for supposing, if the so-called phyllodes are simply flattened 

 petioles which have dropped their blades, that they can attain lengths of "from 

 P in. to 1 ft." (.1. macradenia), "above a foot long, the upper ones A ft." (A. 



