M. C. COOKE, NOTES ON PODISOMA. 261 



aid of the wind) give rise to a totally different fungus, the Rcestelia 

 cornuta, that is to say, that an alternate generation comes between 

 these fungi. They appertain in consequence to a single species 

 (Rcestelia cornuta), and Podisoma {Gymnosporangium juniper •inuni) 

 ceases to be an independent species, and must be considered as 

 synonymous with the first generation of the Rcestelia." 



"The spores (of Raestelia, it is presumed) have been transported 

 upon young shoots of the juniper tree, and have now commenced 

 to produce some mycelium in the bark. There is no doubt that 

 in next spring it will result in Podisoma (Gymnosporangium) juni- 

 perinum." 



This is Dr. Oersted's report of the results of his experiments, 

 and although not prepared to accepo them, as absolutely true until 

 confirmed by other observers, we cannot ignore the fact that some 

 mycologists have at once, and we think too rashly, accepted the 

 conclusions. 



Subsequently the same gentleman, who is Professor of Botany 

 at the Copenhagen University, made other experiments upon other 

 hosts with the spores of Podisoma. He professes, by similar 

 means as in the other instance, to have demonstrated that Podisoma 

 Sabince, and Rcestelia cancellata are alternate generations of the 

 same species.* This Podisoma Sabince is the same as we have 

 called Podisoma fuscum in the present communication. 



Further, he claims to have established the fact that Podisoma 

 clavariceforme (the Podisoma ju nip eri -communis of Fries) is the 

 first generation of Rcestelia lacerata, which thrives upon the haw- 

 thorn and the apple. 



He observes that there are three Rcestelias found in the north, 

 JR. cornuta, cancellata, and lacerata, and all other forms are varieties 

 of these. That three Podisomas are also found in the same region 

 — P. gymnosporangium, juniperi, and fuscvm. And that these are 

 alternate generations, the one of the other. 



Podisoma. Rcestelia. 



gymnosporangium . . . . = cornuta 



fuscum = cancellata 



juniperi = lacerata 



* Oversigt K. Danske Videns. SelsVabs (1867), p. 208, t. 3. 4. Resume du 

 Bull, tin de la Sue. Roy. Danuise des Sciences (1807,, p. 38. Rutanische 

 Zeitung (1867), p. 104. 



