— 26 — 



70. Grimmia apocarpa (L.) Hedw. Dry or moist rocks. Huletts Lg. (Levy); 



Shushan (Dobbin) ; road near Wiggins iron rnine, W. Fort Ann and 

 vicinity of Vaughns, determined by Mr. Kaiser. The sterile Luzerne 

 plants (G. W. Clinton) known as Schistidium Agassizii Sull. & Lesq., 

 reported in N. Y. State Cab. Rep. 20: 405. 1867, were compared by Dr. 

 • Peck, June 23, 1902, with specimens of 5. Agassizii from Lake Superior 

 in the SuUivant and Lesquereux exsiccati. Dr. Peck says, "while it 

 approaches that species closely in its small size and costa ceasing below 

 the apex of the leaves, I conclude from the shape of the leaves that it 

 is rather a form of S. apocarpum. " 



{To he Continued) 



HINTS FOR LICHEN STUDIES 



Albert C. Herre 



There are apparently very few people in this country actively engaged in 

 the study of lichens. Just why this should be so is rather difficult to see, since 

 many lichens are quite conspicuous, either from their size, color, or numbers. 

 Perhaps the greatest obstacle has been the difficulty experienced by the isolated 

 amateur in finding out their names, whereas the numerous manuals of flowering 

 plants readily afford one an easy introduction to the higher plants. 



In this country we have perhaps neglected most the study of the physiologi- 

 cal activities of lichens. We know relatively little concerning the rate of growth 

 of these organisms, and the causes which may make a given species grow to a 

 much greater size in one region than it does in another. My personal belief, 

 based upon observations of lichens over the region lying between Canada and 

 Mexico, Great Salt Lake and the Pacific, is that actual amount of rainfall is only 

 a minor factor, since Ramalina reticulata, easily the largest of North American 

 lichens, reaches its maximum growth with a rainfall of but 16 to 20 inches. A 

 greatly prolonged growing season, high atmospheric humidity but not necessarily 

 much rainfall, and an undisturbed substratum, are probably the three most im- 

 portant growth conditions for lichens. It is such conditions which make possible 

 the almost incredible length which the fibers of Usnea longissima attain in the 

 mountains of Java, and the coast range of Oregon. 



There is room for a thousand enthusiastic nature lovers scattered over the 

 country to take observations for a series of years upon the increase in diameter 

 of the thallus of our common bark- and rock-dwelling lichens. The exposure upon 

 which growth first appears and is most rapid, the growth in sun and shade, as 

 affected by prevailing winds, or other evident variable conditions, are all things 

 which could be profitably recorded, and after sufficient material had been obtained 

 the results should be collated and published. 



The way in which heredity is transmitted in lichens is a field which should be 

 investigated. As suggested by me on other occasions, Mendelian inheritance as 

 exemplified in most organisms is an impossibility. Under the means by which 

 lichens are usually propagated no sexual reproduction with its complex of chro- 

 mosome division is involved. Lichens are in general asexually reproduced, but 



