ACACIAS OP SOUTH-EAST QUEENSLAND. 43 



than usual, ranging from 30-57 /x, in diameter ; in all other 

 wattle stems sectioned, the vessels reach usually t^vdce these 

 dimensions. The sieve tubes show the same peculiarity, being 

 decidedly narrow in transverse section. The. stem is 

 strengthened by old strands of hard bast, pushed out towards 

 the circumference, to form sclerench3rmatous strengthening 

 bands, like the steel laths of reinforced concrete. The phello- 

 derm takes the methylene blue stain very deeply, as does the 

 live cork ; betAveen the two is seen the almost unstained 

 phellogen, some of the cells undergoing mitotic division. 



In the tangential longitudinal section the same structures 

 are seen, small reticulated vessels and tracheides prevailing 

 throughout a great portion of the X3"lem, A\*ith larger dotted 

 vessels in the sap wood. 



II. — Acacia fimbriafa A. Cumi. and ^4. linifolia Willd. 

 (Plate IV.) No support is given to a separation of these two 

 wattles by a study of their internal structure. The supply 

 and arrangement of the t^essels of the xjdem agree in both forms; 

 the medullary rays are similarly strongly marked, the pith 

 is larger in area, relative to the wood, than in many aUied species, 

 and in tangential section the medullary rays show both in 

 xylem and phloem a single row of elongated oval cells. In 

 the deeper layers of the cortex, strands of sclerenchyma are 

 noted, the cavities of the cells almost obliterated by the 

 addition of layers to the cell- walls. Occasionally these strands 

 invade the outer layers of the alburnum. The larger vessels 

 and tracheides are pitted ones ; reticulated vessels are far 

 less numerous than in A. amhlygona. 



In the medullary rays, when passing through the phloem, 

 the cells are shortest in the direction of the ray, the transverse 

 diameter being much enlarged. 



III. — Acacia aulacocarpa A. Cunn.. A. cincinnafa F.v.M., 

 and A. cunninghamii Hook. (Plate III.) These all belong to 

 Juliflorae, and the first and third species have many features 

 in common. In the transverse section of a young twig, the 

 triangular outline at once distinguishes A. cunninghamii, but 

 this means of identification is lost in older branches. Vessels 

 of the xylem of A. cunninghamii range from 70 /it to 140 /m and 

 are the broadest of any acacia examined ; in A. aulacocarpa 

 they vary from 30 jn to 105 /x ; and in ^4. cincintiata have about 

 the same limits. In the first year's stem of cunninghamii, 



