/'ossil Fungi. 95 



" Amon^ these causes, we have placed in the front rank 

 variations of temperature and the hygronietric state of the 

 air. Apparently, at the time of the Carboniferous epoch, these 

 conditions were but little favorable ; the heat and the humid- 

 ity were spread alike over all the surface of the earth ; the 

 seasons had no existence. It was not until the beginning of 

 the Tertiary epoch that these became apparent and were 

 clearly distinguished ; it was only then that the alterations 

 produced in atmospheric conditions can be compared with 

 those that are exhibited at the present time. 



"The paucity of fossil fungi relative to the other vegeta- 

 tion is explained by their soft, fleshy structure, which is but 

 little .liable to become petrified, and soon becomes destroyed 

 without leaving a vestige. 



"Of the crowd of fleshy fungi that exist to-day, very few 

 are known in a fossil .state ; and yet of the former exi.stence 

 of many of them, we have proof in the remains of insects 

 that live upon fleshy fungi to the exclusion of all other 

 substances. 



" It is for the same reason that the greater part of fossil 

 fungi are those known as epiphyllous species. 



" Their bad state of preservation, the impossibilit)^ of sub- 

 mitting them to a microscopic examination, allow a doubt to 

 be cast upon the species and frequently on the genus. One 

 can only determine them by their external form. Even for 

 the epiphyllous species the characters that one finds are 

 reduced to a small number; the general form, the margin, the 

 number of papillae, the umbilicus, or the central monticule, 

 the ostiolum, the furrow, the longitudinal cleft, the surround- 

 ing crown, the color of the perithecia, their mutual arrange- 

 ment, their situation on the upper or the lower surface of the 

 leaves, such are the external characters that one finds for 

 verification, little fit to characterize the species; at the most, 

 suitable for the genera or the orders. 



" It has thus become necessary to limit one's self by connect- 

 ing with the genus Sphcerites [for example], different genera 

 of Sph(£tiacea\ the same with the genus Xylomiies, the differ- 

 ent genera of the family Ustaliginca. 



"For these reasons the author has added to the names of 

 the fossil fungi the final syllable itcs, for the purpose of dis- 



