gg NATURAL HISTORY BULLETIN. 



Endocarfon, Pannaria, Oiiiplialan'a, CoUenia, Vernican'a, 

 are genera which illustrate this feature, nor should two rare 

 Lecanoras be omitted here. 



Of the 196 forms listed, 92 were found only on wood, 57 

 only on rocks, and 26 only on earth; while 15 were found on 

 both wood and rocks, 2 on wood and earth, and 3 on rocks 

 and earth. From this it appears that about 47 per cent, are 

 distinctly wood hchens, 29 per cent, distinctly rock lichens, 

 and 13 per cent, distinctly earth lichens. 



Of those growing only on rocks, 32 were found on calcare- 

 ous rocks, 17 on granitic, 4 on both, and 4 on sandstone. 

 Of those growing only on wood, 71 grow on trees, 14 on dead 

 wood and 7 on both. Again counting those found in two 

 habitats twice, 109 grow on wood, 76 on rocks, and 31 on earth. 

 On this basis 55 per cent, grow on wood. 39 per cent, on rocks, 

 and 16 per cent, on earth. 



Of the genera. Cladonia is largest with 21 forms, Lccaiiora 

 being next with 20, and Biatura following closely with 18. 

 The total number of genera represented in the list is 34. The 

 absence of the genera UmhiJicaria, Pyroiopsis, Stcrcocaiilon. 

 and Caliciiun which are so well represented at the east should 

 be noticed. Also the genera Cctran'a and Sticta. so common 

 in the eastern states, are each represented by a single species. 



Of the lichens herein listed 120 are generally distributed 

 over the United States, 49 are Atlantic, 15 Western, 5 Arctic 

 and sub- Arctic, 4 Southern and 3 Pacific. The small number 

 of Arctic, Southern and Pacific forms is to be explained b}- 

 climatic, geographical and geological causes. Long continued 

 connection with the regions east, as well as the absence of 

 great mountains, are causes which conspire to give us so 

 many Atlantic forms. It needs to be stated that in the above 

 estimate Hchens extending from the Atlantic toward the interior 

 are called Atlantic and those extending from the Pacific toward 

 the interior Pacific, while those found only in the interior are 

 considered western. This explains the small number of west- 

 ern forms given' from a western state. 



