90 R. H. CAMBAGE. 



regarded as abnormal bipinnate than pinnate leaves. In a 

 few species the pinnae increase on some of the succeeding 

 leaves to several pairs, and on many species each succeed- 

 ing bipinnate leaf often produces an increased number of 

 leaflets. 



A well known feature in connection with many species 

 of phyllodineous Acacias is that should the trees be cut 

 back or wounded, bipinnate leaves will often appear, while 

 in a few species, particularly A. rubida and melanoxylon, 

 the older portions of a sound branch may be covered with 

 phyllodes, while without any apparent cause, the terminal 

 leaves of the same branch may be bipinnate, both of the 

 above characters thereby showing a reversion to some form 

 of ancestral foliage. The feature is perhaps more common 

 on suckers than on plants which have grown from seedlings; 

 though so far as observed, an Acacia sucker does not appear 

 to ever produce a simply-pinnate leaf, but the point requires 

 further investigation. Mr. A. A. Hamilton has recorded an 

 instance of a tree fifteen feet high of A. melanoxylon pro- 

 ducing bipinnate leaves on the tips of the phyllodes. 1 At 

 the last monthly meeting of this Society Mr. E. Oheel 

 exhibited a flowering specimen of A. suaveolens showing 

 bipinnate foliage above the fruiting or pod-bearing twigs. 



Phyllodes. 



It is well known that the phyllodes are the cylindrical, 

 dilated or vertically flattened petioles of the bipinnate 

 leaves, and this curious development has apparently taken 

 place in response to environment. For some reason, prob- 

 ably climatic, the plants evolved this form of structure as 

 being more suitable under the existing circumstances for 

 carrying on the functions of leaves than were the original 

 leaves. A study of the seedlings shows that the transition 

 from leaves to phyllodes takes place at different periods of 



1 Proc. Linn. Soc. N.S. Wales, xxxix, 1914, p. 254. 



