^^%'^ Kelly, Concerning Acacia PhvUodes. 121 



from the main nerves as veins from a midril). This is also seen 

 in A. dallachiann and in A. alpina. In A. Doratnxylon the 

 central nerve is more prominent, the others slight. A. con- 

 junctifolia may be a stage between A. Bailey ana and A. verti- 

 cillata, or, indeed, more advanced still. 



The history of one species is, except as to detail, the history 

 of the others. Take, for example, the Golden Wattle, A. 

 pycnantha, as one of the best known. It is conceivable that in 

 its bipinnate form as a full-grown tree it flourished in situations 

 similar to those in which it is now found, less sheltered and less 

 moist than the habitats of the decurrent grouji. In these more 

 open but temperate parts it assumed its first modifications. 

 Then occurred a new exodus. From these the seeds may have 

 been carried farther inland to parts hotter and still less 

 watered, and deposited there in the ejecta of birds. The un- 

 digested seeds, with softened integuments, readily germinated 

 when soil and weather conditions favoured. The young 

 plants were, however, soon in trouble through want of root 

 moisture and rapid evaporation. The delicate leaves fell, 

 but the stem, branches, and leaf-stalks, with their restricted 

 transpiration surface, survived. Later came a new season of 

 growth ; the leaf-stalks felt their way with caution, broadening 

 in the impulse and necessity for aerial feeding, the branches 

 helped by projecting decurrent ridges — ^jury-masts rigged up by 

 nature to weather the storm of circumstance. The device was 

 a good one. Season by season it was elaborated. The em- 

 bedded laminre rarely ventured out in the open, and when they 

 did they failed, as before, to stand the test of intense heat and 

 light. The substitute was more serviceable. As the phyllode 

 extended and fought for breathing space it had to adapt itself 

 to hard conditions. This it did by adopting an oblique droop, 

 turning its edge to the sun. Other species overcame the 

 trouble partly by this means and partly by develoi)ing a 

 waxen bloom on the leaf surface — a sort of curtain against the 

 sun : others by elongating the phyllodes in cylindrical and 

 circular forms. The time came when the emigrant pvcnautha, 

 after many generations in Eremia. came back, y>e\- bird (or 

 otherwise) to Euronotia. and found there the incentive to fuller 

 growth. 



Many of the species as])ire even now, and ha\e long been 

 aspiring, to good form. They intend to have true lea\es. The 

 Golden Wattle, ]iassing through many vicissitudes, has nearly 

 reached its goal. It has almost a perfect lamina and jietiolc ; 

 it has a midril) already ; it has lateral veins, and the sides of 

 the blades are nearly equal. Its mountain relation, A. pcnni- 

 tirrvis, follows rlosely in (levelo|)mcnt. but its halves are not 

 so ecpuil. 15olli trees hang their U\i\-es obliciiu'ly, thus 



