151 



from the area of common distribution northward have helped to 

 keep down any modifications which might otherwise have ap- 

 peared after long continued and perfect isolation under changed 

 conditions ? Mr. Walter Deane gives me the following pertinent 

 quotation from a ** Notice of Flowering Plants and Ferns col- 

 lected on both sides of Davis Strait and Baffin's Bay," read by 

 Mr. James Taylor before the Botanical Society of Edinburgh.* 

 ** S. Jicrbacca, coast to snow line, covers extensive tracts, ^\\<\ that 

 too where most other plants cease to appear, except Jitnci and 

 Liizuhu. In dry fine weather I have often seen its downy seeds 



ift 



might 



be transported a very great distance by a strong upper-current 

 of wind, and the alpine summit of a high mountain, with its sur- 

 face constantly moist and dripping from melting snow-drifts, 

 would present all the conditions favorable for their germination. 

 After this, the gaining and maintaining of a permanent foothold 

 would depend upon climatic influences, to which S. ' herhaeea 

 seems peculiarly sensitive. It is not found on the Rocky Moun- 

 tains, where four at least, of the species with which it is associa- 

 ted in Greenland are widely distributed, though in strongly mod- 

 ified forms. It is noticeably present on all the Arctic shores of 

 the North Atlantic, both American and European ; and just as 

 noticeably absent from all the shores of the North Pacific, both 

 American and Asiatic. It does not vary to meet varying condi- 

 tions, but thrives where these are favorable, and does not grow at 

 all where they are unfavorable. 



Notes upon Zygodesmus and its New Species. 



The genus Zygodesmus is something of a puzzle to the stu- 

 dent of systematic fungology, and therefore does not lack in in- 

 teresting points of structure. Of the twenfy-sevcn species enu- 

 merated by Saccardo,* sixteen are known to be North American. 

 None of these infest growing tissues, and a large percentage, 

 fully twenty out of the twenty-seven, arc found upon dead wood 

 or bark. It is interesting, therefore, to note that a new species 

 was found early last summer near New Brunswick, N, J., upon 

 the flower-bearing stems of Pyrola rotundifolia, namely Zygodes- 



*Trans. Vol. 7, 1862. 



