ao Feb., 1911.] Phosf/ioric Acid ui Ixdation to Sals ond Vegetation. 



surface of the soil in the excrements. As the phosphoric acid becomes 

 available in increasing quantities, in the surface soil, the growth of plants 

 is stimulated, and consefjuently larger numbers of land animals are carried 

 on to a given area. It will thus be seen that the history of phosphoric 

 acid in the surface .soil is very similar to that of the phosphatic rocks, 

 and also of most limestones. In the latter cases, the phosphoric acid 

 and the lime have been slowlv concentrated from the waters of the sea 

 by the action of plant and animal life combined in tlie one case, and 

 animal life alone in the other. 



From observations that have been made on a moie restricted scale 

 in the other Australian States, there seems to be little doubt that what 

 holds true in Victoria applies to Australia generally, as far as regards 

 the small amount of phosphoric acid in the surface soil. 



I take it that the .small percentage of phosphoric acid in our surface 

 soil is due to the fact that the Continent has never been heavily stocked 

 by large animals of anv kind. In Victoria we know that, previous to 

 settlement bv w^hite men, the number of kangaroos and emus was much 

 less than the number of sheep is at present. Taking the Continent all 

 through, there seems little doubt, from the accumulation of the bones 

 of existing and extinct species in the mud of many lakes in the interior, 

 that periodical droughts have kept down the numbers of animals during 

 recent geological epochs. In Victoria vast areas were so densely tim- 

 bered that it is certain that herbivorous animals were never present in 

 large numbers ; for it is found that browsing animals keep down the 

 forests, not by destroying the large trees, but by preventing seedlings 

 from growing and taking the places of the forest trees which die from 

 old nge. In the ca.se of the Island of St. Helena, this action has been 

 sufficient to completely destroy the original fore.sts in less than ;^oo years. 



Adapt.ation of the Native Herbage to Special Conditions. 



While carrying on the investigations into the phosphoric acid content 

 of our poorer soils, I was struck by the fact that certain forms of native 

 vegetation are found on nearlv all the soils in question, and that allow- 

 ing certain modifications for the rainfall one might form a verv good 

 estimate of the amount of phosphoric acid present in anv given area bv 

 the vegetation growing thereon. The following table gives the per- 

 centage of phosphoric acid in a number of these characteristic plants: — 



In the above analy.ses the green lfa\«s flowers and seeds were used for 

 analysis, woorly fibrous stems and roots Yte'mg excludefl. except in the ca.Sf* 



