OF ARTS AND SCIENCES. 311 



XIII. 



NOTES ON SOME SPECIES OF GYMNOSPORANGIUM 

 AND CIIRYSOMYXA OF THE UNITED STATES. 



Br W. G. Farlow. 



Communicated February 11th, 1885. 



In a paper published in the Anniversary Memoirs of the Boston 

 Society of Natural History in 1880, I gave an account of my attempts 

 to show, by means of cultures, the relationship of the Gymnosporangia 

 found near Boston to the different forms of Rcestelia occurring in the 

 same region ; and also, by reviewing the geographical distribution of 

 the species of both genera in the United States, to ascertain the prob- 

 abilities of the genetic connection of different forms of the genera in 

 question. My cultures, however, were not successful in proving the 

 direct relationship of any given Gymnos-porangium with any given 

 Rcestelia ; but, as the subject is of importance, both from a biological 

 and practical standj^oint, I have made further attempts to see whether 

 a more definite result could be reached. 



The method of culture employed was the following. Specimens of 

 different species of Gymnosporanglum were gathered early in May, 

 before the spores had begun to germinate, and while the spore masses 

 were flat and not swollen in gelatinous protuberances, as is the case 

 when they are moistened by showers. The specimens were then 

 placed in watch-glasses under moistened glasses, each species by itself, 

 when the spore masses soon expanded, and the spores began to ger- 

 minate. It was in this way easy to arrange so that the spores of the 

 different species were kept pure, — a fact coniirmed by microscopic 

 examination. As the spores germinated, the sporidia, of a bright 

 orange color, dropped into the moist watch-glasses, and were used at 

 once for infecting the desired plants. Two kinds of material were 

 used. The first consisted of leaves of different Potnaceae, which were 

 freshly gathered in the Botanic Garden of Cambridge, and at a dis- 

 tance from any species of Jnniperns which could have been infested 

 by a Gymnosporanglum. The leaves were placed on moistened glass 



