6 FARLOW ON THE GYMNOSPORANGIA 



MiCROPUCCiMA. Only teleutospores . known. Spores quickly detached but not ger- 

 minating except after a considerable interval. 



Leptopuccinia. Only teleutospores known. Spores persistent, germinating quickly. 



From the above named divisions it is evident that there is no want of variety in the 

 genus Puccinia, or perhaj^s it would be better to say that there is a very considerable 

 ignorance of the forms which may occur. Turning from Pucciuia to other genera of the 

 order, in Uromyces, of which the teleutospores differ from those of Puccinia in being one- 

 celled, we have the same variations in the presence or absence of the different stages and 

 Schroeter divides the genus in a similar way, into Euromyces, Hemiuromyces, etc. In 

 the genus Gymnosporangium, which differs from Puccinia in its gelatinous nature, only 

 aecidia and teleutospores are known. In Cronartium aecidia are unknown. In all the 

 genei-a the teleutosj^ores are supjiosed in germinating to jn'oduce the characteristic pro- 

 mycelium and sporidia, although as I shall have occasion to remark later, this is subject to 

 modification, while the aecidial spores and stylospores germinate by giving out one or 

 more germinal filaments as is the case with the spores of most fungi. In the aecidia the 

 spores are always either orange colored or brownish, and are formed in chains which arise 

 from a sort of placenta formed by the mycelium, at the base of the cellular sack known 

 as the i^eridium. Spermogonia are present in the aecidial stage, and are developed 

 earlier than the cups, or aecidia proper. The relative abundance and jiosition of the 

 spermogonia with respect to the aecidia themselves, vary in the different species. They 

 are sometimes on different sides of the leaves, as in Puccinia Graminis, sometimes mixed 

 rarely on different parts of the plant. The uredo forms of the different genera vary more 

 than the aecidial forms. As a rule the spores are borne singly, but in some genera, as 

 Coleosporium, they are in chains. The so-called peridium found in the aecidia is 

 wanting in the uredo forms, but there is sometimes a false peridium fonned from the cells 

 of the host plant, or the spots are surrounded by a circle of sterile cells, called paraphyse.s, 

 derived directly from the mycelium. Spermogonia are usually wanting, but are found in 

 a few cases. The teleutospores of the different genera vary greatly in several respects ; 

 they may be unicellular, as in Uromyces and Melampsora ; two-parted, as in Puccinia and 

 Gymnosporangium ; or many-celled, as in Phragmidium and Xenodochus. They may 

 vary from gelatinous, as in Gymnosporangium, to dense and indurated, as in Melampsora. 

 They may rise above the surface of the host plants in columns, as in Cronartium, or may 

 be sunk among the epidermal cells, or even produced within them, as in Melampsorella. 

 The principal generic distinctions are derived from the characters of the teleutospores, but 

 as far as possible, continental writers have regard to the respective aecidial and uredo 

 forms. The genera are perhaps not in all cases well marked, but they are at least quite 

 aa well defined as in the other orders of fungi. 



In studying the Uredineae of the United States, one, for several reasons, naturally begins 

 with the genus Gymnosporangium. The species of the genus are comparatively ievf in 

 number, and are, with us, found only on different Cupressineae. The teleutospores occur 

 in spring or early summer, and resemble those of Puccinia in being generally though not 

 always two-celled, but differ from them in being borne on very long hyaline stalks, the 

 whole being imbedded in a mass of jelly which in moist weather swells up and forms the 



