^m2'] Kklly, Concerning Acacia Phyllodes. 123 



evaporating surface, but be reduced in size. The acicular and 

 other small phylloded forms never produce pinnate leaves after 

 the infantile stage, indicating a much longer period after the 

 change than would be attributed to, for instance, A. melan- 

 oxylon. When the A. verticillata, A. diffusa, and A. jtmiperina 

 types, after their sojourn in the wilderness, were brought back 

 to the land flowing with water, they had neither physique nor 

 size to support, and what they lacked in individual leaf surface 

 was easily recompensed by increase in number of small surfaces. 

 Coming into close bush association, they were more able to 

 compete with encompassing growths than they would have 

 been had they reverted to the pinnate type, or developed 

 ])road jihyllodes, with the necessity of acquiring a new code 

 of phyllotaxis or leaf adjustment. They could grow where 

 they found a foothold, and knew little necessity for elbow-room. 



The conclusions to which I am drawn are that we can claim 

 to trace our many species of acacias in speculative fashion back 

 to a common form, to A. farnesiana as the earnest known 

 representative of the bipinnate acacias. That was probably 

 preceded by a simple-leaved legume whose history is only to 

 he learned from geology or embryology. A change of environ- 

 ment produced the phyllodinous type in numerous variations, 

 now specific. Some of these, doubtless, by perfecting other and 

 less i)lastic organs, have reached a finality of development, 

 particularly those linear and spinescent types which have 

 carried their desert forms back to moist regions. The broad 

 phylloded types are in a present progressive stage, either 

 fixing the new character or gradually adopting simple and 

 entire leaves with an enclosed venation. There are inter- 

 mediate i)hases suited to the general develo])ment of the plants 

 which may be regarded as stationary, and in considering this 

 subject it must be remembered that one of the ]-)rincipal uses 

 of veins or nerves to the leaf is suj^port. For leaves held in a 

 vertical position or hanging obliquely, the longitudinal veining 

 would give better service. Where leaves require a surface 

 spread to the sun they need ribs like an umbrella. Most of 

 the sul)stitute leaves or phyllodes of acacias have adopted the 

 oblique ha])it, and with it suitable vein support. In this change 

 they have done away with the leaf-sleeji or folding habit of 

 mimosa. 



Though thc> results of my investigation, both of materials 

 and books, may be crude, it has given me much pleasure, and 

 I am convinced that, as the potentiality of man is only limited 

 l)y his ambition and desire, so is that of plants by their 

 necessities. Every plant has embodied in it the eh^ments of 

 man's caj^acity to {progress or regress, limited only to its needs 

 as a plant. It is not a necessity of a plant to develop beauty 



