198 COMPENDIUM OF GENERAL BOTANY. 



grain-fields. 3. Grasses growing wild in the grain-fields (example : 

 Triticum repens) often serve as hosts to the fungus. These must 

 also be destroyed. 



The course of development in Puccinia graminis is as follows : 

 (a) The fungus lives upon the leaves of Berberis vulgaris during 

 the spring and produces seeidiospores (Fig. 123, 7&, A), which 

 are carried to the wheat- or oat-plants by the wind ; (&) germina- 

 tion and growth begin at once and end with the formation of 

 uredospores, which may be carried to other plants and also develop. 

 (The spermagonia and spermatia shown in Fig. 123, sp, are little 

 understood. Formerly they were supposed to be male sexual 

 organs. 1 ) The earlier che fungus attacks the plants the more in- 

 jurious are the effects. Sometimes all the leaves are infected, even 

 the glumes. Toward the close of the vegetative period (<?) teleuto- 

 spores are formed, which remain at rest during the winter months 

 and begin to germinate in the early spring. From them grows (d) 

 &promycelium with sporidia. The sporidia develop upon suitable 

 hosts (in this case upon the leaves of Berberis) and again form 

 secidiospores, thus forming the beginning of a new cycle of 

 development. 



Tilletia Caries causes the smut of wheat; various species of 

 Ustilago cause the blight of different grasses, especially of oats, 

 barley, and wheat. (To prevent the occurrence of both of these 

 fungi it is necessary to soak the seed to be sown in a J per cent 

 solution of sulphate of copper for about twelve or fourteen hours 

 and then to sow the seed during dry weather.) In this disease 

 spore-formation takes place in the ovarium with destruction of the 

 ovulum, while the assimilating organs (leaves and stems) are not 

 attacked, as in rust-diseases. The spores adhere to the outside of 

 the seed ; hence it is advisable to soak it in a copper-sulphate solu- 

 tion of sufficient strength to destroy the spores without destroying 

 the germinating powers of the seed. The group of fungi to which 

 Tilletia belongs develops conidia upon basidia which are peculiar 

 in that they arrange themselves in the form of an II before develop- 

 ing into a mycelium, which again produces rust-spores. 



In conclusion we w r ill mention reproduction in a fungus from 

 the group of Ascomycetes, namely, Clavipes purpurea, usually 



1 See foot-notes on pp. 189 and 200 in reference to spermagonia of lichens. 

 TRANS. 



