NORTH AMERICAN FUNGI. 43 



signed to the localities in the proposed lists and Flora. For Agarics 

 and other fleshy fungi, drawings and sections will be necessary, 

 accompanied by spores. For known and named species, some 

 method of compensation will be devised, in the form of an equal 

 number of named European species, to be sent to contributors. 

 As so much depends on the co-operation of American Botanists to 

 render this venture successful, it is hoped that they will make an 

 effort in such a national work, and place themselves at once in 

 communication with the Editor of this Journal. 



N0STOC AND COLLEMA. 



By Professor Horatio Wood, M.D. 



In his work on the Freshwater Alg£e of the United States Dr. 

 Wood thus alludes to the Collema question : — 



As no sexual reproduction has as yet been shown to exist 

 amongst the Nostochacece, it is very evident that their whole life- 

 history is not comprised within the changes detailed. It h^s long 

 been known that the gonidia of many lichens have the poWer of 

 independent existence, i.e., that when they are discharged from their 

 thallus they can continue to live and multiply, if circumstances 

 favour them, without giving origin to a new thallus. This and 

 the great similarity of structure between the Nostocs and the 

 lichen genus Collema has suggested a .possibly close relation 

 between the two. The first observer, I believe, who asserted that 

 they were different stages of the same plant was Dr. Hermann 

 Itzigsohn. His observations are, however, rendered of little value 

 by his own statements. The most weighty observations upon this 

 subject are those of Professor Julius Sachs and of J. Baranetzky, 

 the former published in the " Botanische Zeitung " for 1855, the 

 other in the " Bulletin of the St. Petersburg Academy " for 1867. 



Professor Sachs states that he watched a whole bed of Nostoc 

 commune developing into Collema pulposum. He says that the 

 peculiar coUemoid threads first appeared as little lateral offshoots 

 or prolongations from the cells of the Nostoc filament, and rapidly 

 developed into well formed collemoid filaments. Every possible 

 stage from the typical Nostoc to the typical Collema was seen re- 

 peatedly. The development of the distinguishing threads of the 

 Collema out of the ordinary Nostoc-cell has never been confirmed 

 by any other observer ; but it seems to me that it must be at least 

 provisionally accepted, although De Bary expresses some doubt of it. 



The researches of M. Baranetzky were directed to the develop- 

 ing of a Nostoc out of a Collema. Hicks and other observers had 

 previously stated that they had seen this, but none of them had 

 given sufficient details as to the method of their observations to be 

 fully convincing. M. Bai'anetzky placed sections of actively grow- 

 ing fronds of Collema pulposum upon smooth damp earth, using all 



