OP ARTS AND SCIENCES. 259 



XIV. 



CONTRIBUTIONS FROM THE CRYPTOGAMIC LABORATORY 

 OF THE MUSEUiM OF HARVARD UNIVERSITY. 



VII. — ON CERTAIN CULTURES OF GYMNOSPORAN- 

 GIUM, WITH NOTES ON THEIR RCESTELI^. 



By Roland Thaxter. 



Presented December 8, 1886. 



In a paper entitled "Notes on some Species of Gymnosporangium 

 and Chrysomyxa of the United States," communicated to the Academy 

 in February, 1885, Prof. Farlow gave an account of certain cultures 

 conducted by him with a view to determine the relation of the species 

 of Gymnosporangium found in this vicinity to the different Rosstelice 

 growing in the same locality ; and it is the object of the present paper 

 to supplement these observations by an account of further experi- 

 ments on the subject undertaken by the writer while studying in Prof. 

 Farlow's laboratory during the past spring. 



The more important results obtained have already been published 

 in an article read by Prof, Farlow before the American Association 

 for the Advancement of Science, at Buffalo, and contained in the 

 September number of the Botanical Gazette ; yet a somewhat more 

 detailed account may be of interest, together with some further obser- 

 vations on the species of Rcestelia which may serve to explain several 

 doubtful points in this connection. As a guide also to those unac- 

 quainted with the cycle of development of these fungi, it may not be 

 amiss, before considering the cultures, briefly to summarize it. 



The species of Gymnosporangia, or cedar apples as they are popu- 

 larly known, are fungi parasitic upon certain cedars, — in this vicinity 

 Juniperus communis and Virginiana together with Cupressus thyoides 

 being the species attacked, — upon which they produce distortions 

 more or less characteristic in appearance. At maturity, towards the 

 close of spring, the fungus consists of certain sporiferous masses 

 emerging from the distoi'tions produced by the growth of its mycelium 

 in the stem or leaves of the host plant. "When moistened, these 

 masses expand to many times their former size, becoming soft and 



