2 30 PLANT LIFE. 



and deformed cavity in the trunk with raised edges. 

 It has been stated that this canker fungus of trees is 

 identical with the cancer which attacks mankind. M. 

 Bra claims to have produced cancer in rabbits from the 

 spores of this fungus, and also to have produced canker 

 in trees by infecting with human cancer. 



Amongst other important fungi in the Pyrenoinycete 

 group are Ergot {Claviceps), which grows in the ovary 

 of the rye ; and if eaten when ground up with the 

 grains, produces paralysis, decay of the toes or fingers 

 and other horrible effects. The Tuberaceae^ or Truffles, 

 are subterranean fungi found in rich humus under 

 trees. The fruit is a more or less rounded body 

 containing many cavities in which are the asci and 

 spores. 



The Eust and Smut Fungi {Aecidioniycete and Ustila- 

 gineae)^x^ more easily found and named than the preceding 

 groups. They produce some of the most dangerous 

 plant diseases, and seem to have a special partiality 

 for settlers' crops in newly opened countries. They 

 are generally easy to see, as the orange or brown 

 stripes or spots attract attention. The plant attacked 

 is also different from other plants of the same kind, 

 it is more sickly-looking and often yellower than its 

 neighbours. If one passes slowly through a field of 

 thistles, unhealthy specimens, with leaves more upright 

 than usual, and covered with brownish-red spores on 

 the under surface, are easily distinguished. The fungus 

 attacking thom is Puccinia suaveolens whose spores have 

 a distinct odour, rather like that of the Evening Primrose. 

 Coltsfoot leaves also are often covered witli conspicuous 

 red spots on the under surface, especially where the 

 plant grows in great numbers. But almost every plant 

 has its own special rust-fungus, and many a smut- 



