CHAPTER i 

 STOCK-KILLING PLANTS 



The injurious plants of country and farm may be divided for conven-* 

 ience of treatment into those which cause -physical injuries to animals 

 and to man in a mechanical way and into those which cause injury, disease, 

 or death by some deleterious, or poisonous substance possessed by the 

 plant. The former have been termed stock-killing plants and the latter 

 poisonous plants. There is no sharp demarcation between the two kinds 

 of plants, but the distinction has proved to be a useful one. 



The first group includes those plants which are mainly harmful to 

 cattle, causing serious troubles, which may result eventually in the death 

 of the animal. This group includes a considerable number of species 

 none of very close taxonomic relationship. The anatomical and mor- 

 phological peculiarities upon which the injury depends are very diveise 

 and consequently they become active in a great variety of ways. 



Aspergillus fumigatus. This grayish-green mould fungus was first 

 discovered by Fresenius in the bronchial tubes and air cavities of the 

 bustard. The fungal herbage on culture media is greenish turning to gray 

 and even to dirty brown. It is readily identified by the short conidio- 

 phores (0.1-0.3 mm ' l n g) with club-shaped extremity and simple upright 

 sterigmata forming long chains of very small (2-3 ju), globular conidio- 

 spores. True perithecia are known with thin-skinned asci and light-red, 

 lenticular, tough-skinned spores (4-4.5 ju) surrounded by a pale, radially 

 striped, .equatorial band. The fungus grows at a high optimum tempera- 

 ture (about 4oC.) and hence is well adapted to thrive in living animals at 

 blood temperature. 



Pathogenicity. It causes pathogenic conditions in animals and man by 

 growth in the lung tissue and in the air passages, where its presence causes 

 difficulty of breathing and develops a toxin comparable to the toxins of the 

 bacteria. Death may be caused by the filling of the air cavities which 

 leads to the final asphyxiation of the host, as well, as to a generalized 

 affection similar to hemorrhagic septicemia. It occurs in the human ear 

 producing otomycosis, and in the bronchi (bronchomycosis), and in the 



