XX. ABSTRACT OF PROCEEDINGS. 



capital than the land is worth ; in many cases as land 

 becomes divided into smaller areas and more under control, 

 and more labour to work it, it will disappear, as an aggres- 

 sive pest, like the rabbit. At the same time whenever it 

 appears in a fresh place, war should be ruthlessly waged 

 against it. Mechanical means of eradication seem to be the 

 best, and chemical means to be subsidiary. Experience has 

 shown that the best prickly pear killers contain arsenic as 

 an active ingredient, a substance well known as poisonous 

 to all vegetable and animal life. White arsenic is almost 

 insoluble in water, but it readily dissolves if treated with 

 caustic soda, and landowners should make their own weed- 

 killers, and save the enormous profits of the man who simply 

 does the mixing up. 



By far the greater problem is the eradication of existing 

 noxious prickly pears. Experiments have been made in 

 the direction of obtaining a non-prickly pear, or a spineless 

 cactus, as it is sometimes called. My own early experi- 

 ments followed the lines, to some extent, of the late Prof. 

 K. Schumann, of Berlin, the greatest authority on this 

 group of plants in his day. But he laboured under the 

 disadvantage of experimenting under unnatural conditions, 

 since Germany is too cold for these plants to develop 

 naturally. On my visit to Europe in 1900 I consulted 

 Professor Schumann, and also inspected the principal col- 

 lections of Opuntia in Europe. I brought to Australia 

 specimens of the true inermis, given to me by Professor 

 Schumann as the proper species from which it was most 

 likely I should get a spineless form. In the genial climate 

 of Australia it soon developed spines, and when it flowered 

 and fruited I found that it was the same as the principal 

 prickly pear which is such a pest in New South Wales and 

 Queensland. I accordingly turned my attention to the so- 

 called Indian fig {Opuntia fiens-indica), one of the principal 



