460 SYSTEMATIC BOTANY. 



Teleutospores. 

 ^Ecidium-spores accompanied by sperrnogonia. 



Uredospores, and later on the same mycelium 

 teleutospores again. 



ILLUSTRATIVE GENERA : Puccinia, Lk. ; jEridium, Lk. ; Uromyces, Lev. 



Structure and Life-history. The life-cycle of these parasites begins with 

 the germination of the teleutospores thick-walled spores situated at the 

 end of filiform basidia, either singly or in pairs, according to the genus to 

 which they belong. The germination takes place in spring, and consists 

 in the emission of a germ-tube, which rapidly forms a promycelium bearing 

 three or four sporidia. These sporidia also soon push out germ- tubes, which, 

 if on a suitable host-plant, penetrate the epidermis-cells and form a myce- 

 lium within the parenchyme. After a few days this mycelium begins to 

 form a new fructification under the epidermis of the host-plant, which even- 

 tually breaks out under the forms of the ^Ecidia and their constant com- 

 panions the spermogonia. The latter appear first. Round them, or 

 irregularly among them, are the ^Ecidia. The spermogonia are in shape 

 small narrow-necked sacs of the same colour as the ^Ecidia. They were 

 formerly believed to be different species of Fungi from the ^Ecidia, but 

 Tulasne has shown that they belong to the same. In them are found 

 minute bodies, called snermatia, which Tulasne believed to be male 

 organs (spermatozoids), since he found them incapable of germination ; 

 but no female organs have as yet been found. It was also suggested that 

 they stood in a sexual relation to the ./Ecidia, near which they are con- 

 stantly found ; but Professor de Bary has cultivated true ^Ecidia, the 

 spores of which germinated, on a plant on which was found no trace of 

 spermogonia or spermatia. The subject is at present wrapt in mystery. 

 The ^Ecidia consist of at first round or oval, and after bursting* basin- 

 shaped receptacula, the walls of which are composed of pseudo-paren- 

 chyme (short, polyhedral, closely fitting mycelium-cells). At the base of 

 this body is the hymenium a circular layer of short, cylindrical, club- 

 shaped upright basidia, on each of which rests a series of spores in regular 

 order, one above the other. The spores are of a round polyhedral form, 

 and filled with protoplasm coloured red or yellow by oil. On the burst- 

 ing of the enclosing peridium of pseudo-parenchyme the spores are libe- 

 rated in a state capable of germination, which takes place in the form of 

 short crooked germ-tubes that penetrate through the stomata of the next 

 host-plant, and form rapidly a new mycelium in the intercellular spaces. 

 Again, after a few days, this mycelium forms a new fructification the 

 Uredo. The Uredo is at first of "the shape of a flat circular cushion lying 

 immediately under the epidermis of the affected part. On it arise filiform 

 basidia, each of which bears a round or oval spore the Uredospores, which 

 during their formation break through the epidermis. The Uredospores 

 germinate rapidly and reproduce themselves constantly, and to this quality 

 is the rapid and extensive spreading of this disease to be attributed. The 

 same mycelium which begets the Uredo, afterwards forms the teleuto- 

 spores from which we started. The teleutospores hibernate and germinate 

 again in spring, as we have seen, and so every year the disease passes 

 through the same cycle of generations. 



