THE VICTORIAN NATURALIST. 45 



for wherever wheat is grown there the rust is found. In 1889, 

 a bad season for rust, the loss for the whole of Australia was 

 estimated at between ;^2, 000,000 and ;^3, 000,000. In 1891 

 the loss in the United States was placed at ^^i 3,000,000, while 

 in Prussia, for the same year, the loss in cereals was calculated 

 at ^20,000,000. The annual loss in India is estimated in some 

 seasons to reach a total of ;!^2, 000,000, and if we take into account 

 other countries where the loss has not been calculated, you can 

 readily understand that the grand total would astonish even those 

 who know something of the destructive effects of rust in general. 

 At a low estimate it is considered that ^100,000,000 does not 

 cover the annual loss to cultivated cereals alone. 



But it is not only our cereal crops that are liable to rust. The 

 fruit trees in our orchards, the wattle trees in our plantations, 

 and even the ornamental plants of our gardens are attacked, 

 and their study is not only interesting from the point of view of 

 the scientist, but from that of every grower of plants for pleasure 

 or for profit. It was a rust which practically exterminated the 

 coffee plantations of Ceylon, and the Chrysanthemum Rust, which 

 has been imported into New South Wales, may prove a serious 

 matter to growers if it spreads. 



Enough has been said, I think, to show the great importance 

 of rusts both from an economic and scientific standpoint, ai.d it 

 will now be necessary briefly to consider their nature and mode 

 of life. 



Nature and Mode of Life. — The rusts are parasitic fungi — that 

 is to say, they do not possess the leaf-green or chlorophyll like 

 ordinary plants, and as a consequence they cannot get their food 

 from inorganic material, but are compelled to obtain it from 

 living sources. They are accomplished parasites, and have 

 specialized along this particular line of obtaining food until they 

 have become perfect adepts in living at the expense of other 

 organisms. Their structure is well adapted to their habit of 

 life. The fungus-threads, or mycelium, as it is called, spread out 

 among the tissues of the living plant and absorb nourishment, 

 and when a particular area has been drained of its supplies 

 then the fungus provides for the future by giving rise to the 

 reproductive bodies or spores. 



While the mycelium or absorbing portion is within the plant, 

 the spores burst through and appear on the surface, and it is 

 these bodies which give the characteristic appearance to the 

 rusts, and from which they are named. Sometimes, however, 

 the spores are buried in the tissues of the host-plant, and 1 have 

 seen this occur in the case of the Peach Rust, when they were 

 embedded in the decaying fruit. 



The story of the spores is the story of the rusts, and a study 

 of the different forms makes up their life-histories. The spores 



