The Gymkosporangia oe Cebar- apples op the United States. 



Bt W. G. Farlow. 



IHE UREDINEAE or rusts include a. large number of species which are parasitic on living 

 plants, and, if we adopt the modern view as to their development, they are remarkable for 

 the transformations they undergo, which suggest rather the metamorphoses familiar to us 

 in insects than the ordinary phases of plant life. By earlier writers, the Uredineae were 

 divided into different genera, which were supposed to be distinct, and not genetically con- 

 nected with one another. Thus, for instance, there were the genera Puccinia, Uredo, and 

 Aecidium, each containing a large number of species. That species of certain genera 

 usually preceded or accompanied species of other genera, as Puccinia, was well known, but 

 the two were not supposed to have any genetic connection, and the relation between them 

 was regarded as either quite accidental, or else cases of parasitism. 



In 1848 Gasparrini^ observed the mode of germination of the spores in Podisoma, a 

 genus closely related to Puccinia, and in 1854, Tulasne^ extended the observation to the 

 spores of several other genera of Uredineae. He also advanced the opinion that the so-called 

 species of Uredo, Trichobasis, Lecythea, and related genera were merely early stages in the 

 development of species of Puccinia, Phragmidium, Melampsora, etc. In a paper by De 

 Bary,^ published in 1863, it was maintained that not only were the species of Uredo and 

 their allies forms of development of other genera, but that the so-called species of Aecidium 

 as well were not distinct, but that they too represented stages of development of Puccinia, 

 Uromyces, and other genera, and in point of time preceded the stage described by Tulasne 

 as the stylosporic or uredo condition. The papers of Tulasne and De Bary, as might be 

 supposed, gave a fresh interest to the study of the Uredineae and, while previously mycolo- 

 gists had been mainly occupied with describing large numbers of species based on the 

 microscopic character of the spores and the gross appearance of the spots produced in the 

 hostrplants, after the appearance of the two papers mentioned it became the fashion to try 

 to ascertain the genetic connection between the different forms known as Aecidia and 

 Uredines and the different species of Puccinia, Uromyces, etc. The views of De Bary 

 and Tulasne were, as a general rule, accepted by all the leading mycologists of the con- 

 tinent, but were not so readily received by those of Great Britain. At the present day, the 



1 Osservazioni sulla generazione delle spore nel Podisoma " Recherches sur le developpement de quelques champig- 

 fuscum. Eendioonto R. Aocad. Soienze Napoli, 1848. nons parasites. Aniiales des sciences naturelles. 4 Serie. 



2 Seoonde memoire sur les Uredindes et les Ustitagin^es. Tome 20. 

 Annales des sciences naturelles. 4 Serie. Tome 2. 



