400 E. C. ANDREWS. 
divergent paths followed by various organisms in their 
attempts to defend themselves against the same inorganic 
forces to which they are opposed. 
Nervosze.—A. melanoxylon and A. implexa, in the Ner- 
vosee, are Pleurinerves with globular heads and phyllodes 
with strongly-marked and parallel nerves. Their history 
has been somewhat parallel to that of the Racemose, with 
the exception that the soil chosen was richer than the 
barren and sandy soil chosen by the Racemoseze. A wet 
and cool to cold climate was also chosen. A. melanoxylon, 
the Tasmanian blackwood, commonly grows into a large 
and handsome forest tree. In the youthful stage, up toa 
height of ten feet in certain cases, it possesses bipinnate 
foliage; and, as with the Racemose, both it and A. implexa 
probably migrated northwards along the late Tertiary high- 
lands during the Glacial Period. Mr. R. H. Cambage, in a 
paper read before the Linnean Society of New South Wales 
in 1901, (see page 202 of the Proceedings for 1901) mentions 
the occurrence of outliers of A. implexa on hills in subarid 
New South Wales. These, in his opinion, suggest a con- 
traction of habitat for this species, owing to climatic 
change. In this opinion I concur. 
Tetrameree.—These are Pleurinerves with flowers in 
cylindrical spikes. The corolla has four petals. Bentham 
includes A. cochliocarpa in Tetramerz, evidently because 
of the tetramerous flowers; but the pod is distinctly unlike 
that of the other members, and the geographical station is 
against its inclusion in this sub-series. It would be advis- 
able to exclude it from this group, which developed in the 
extreme south-eastern portion of Australia, and in common 
with A. melanoxylon, A. implexa, and other types, appears 
to have spread to South Queensland during the cosmopolitan 
Glacial Period of the Pleistocene. A local differentiation 
occurred in the Southern Alps, and this gave rise to forms 
