APPENDIX D. Ixxvii 



absence of crust, to say whether we have a Lichen or a 

 Fungus before us.' 



The variability of Fungi under the influence of different 

 external conditions is well known, though the full extent to 

 which this occurs is only gradually being ascertained as a re- 

 sult of special experimental researches on their development. 



The Rev. M. J. Berkeley, speaking of the Hymenomycetes 

 proper, says 1 : ' The members, however, of which this vast 

 collection of plants is composed, are connected so intimately 

 with one another, and the whole mass is so natural, that it is 

 scarcely possible to say where one genus ends and where one 

 begins. Practice alone, and tact, can do this in the more 

 difficult cases; but it must be confessed that in different 

 states the same species is often positively referable to three 

 or more distinct genera, and it is only the possession of in- 

 termediate states which can put one in a condition to say 

 which is the correct nomenclature/ With regard also to the 

 different forms assumed by Fungi, Dr. Lindley says 2 : ' If 

 what is stated above respecting the true nature of ergot be 

 correct, the Oidium abortifaciens must be a second form of 

 fruit, in accordance with many facts observed lately in fungi. 

 Fries long ago announced the fact, that several genera sup- 

 posed to be distinct are in fact merely different modes of 

 fructification, as Cytispora of Sphceria, Dacrymyces urttcce of 

 Peziza fusarioides, &c. 3 These views were, however, con- 



1 Introduction to 'Crypt. Bot.' p. 357. 



2 Vegetable Kingdom,' (srd edit.) 1853, p. 449. 



3 Speaking on this subject previously, Dr. Lindley said (loc. cit. 

 P- 35) : 'That it must be a matter of extreme difficulty to form any 

 precise opinion concerning Fungi, without long experience, will be 

 apparent from the observations of Fries upon the genus Thelephora.' 

 (Elenchus, p. 158.) He asserts that out of mere degenerations or im- 

 perfect states of Th. sulphurea, the following genera, all of which he has 

 identified by means of unquestionable evidence, have been constructed, 

 viz., Athelia of Persoon, Ozonium of Persoon, Himantia of Persoon, 

 Sporotrichum of Kunze, Alytosporium of Link, Xylostroma, Racodium 

 of Persoon, Ceratonema of Persoon, and some others. Th. Fr. Nees von 



