CLAVIS AGARICINORUM. 195 



favour thnt it displaces from the order generally adopted only two sub- 

 genera, Pleiirotiis and Crepidolits ; the former is usually, but apparently 

 without reason, placed after Mycena or Omphalia, and the latter alter 

 Galera. Pleurotns, as Fries himself says, is closely allied to Tricholoma 

 and ClUocyhe ; it is, in fact, only a Tricholoma or Clitocybe growing on 

 trees and stumps instead of on the ground. Its proper position, then, 

 undoubtedly is after Clitocybe. Its peculiar habit is not sufficient to 

 separate it from this group, as we find a habit precisely the same in 

 Armillaria, PJioliota, and Stroj)liaria. For convenience, it would be 

 well to retain the resupinate species in their present position at the end 

 of the subgenus. In the use of this table it may seem a question 

 whether the sequence of the species should follow the vertical or tiie 

 horizontal lines ; the alliance is certainly greater in the horizontal series. 

 For instance, Armillaria is much nearer to PhoUota and Stropharia 

 than to Tricholoma ; in the former the structure and the Jiabil are the 

 same, the spores only are different in colour. A reference to the cha- 

 racters of the subgenera in part 3 of this essay will show that this is 

 true of all the other subgenera. I do not, however, propose to adopt 

 this system, though Fries has used it in arranging the genera of the 

 Agaricini, for after Agaricics he places Coprinus, wholly disregarding 

 the spores, and depending on the structure, which resembles Lepiota ; 

 then follows Cortinarius, resembling Armillaria, Tricholoma, and their 

 allies (see table); then Paxillus,\\\\h. the gills decurrent as in Clitocybe; 

 and so on, in accordance with structure and habit, to the end of the Order. 

 Had the genera of Jgaricini been arranged after the manner of the sub- 

 genera of Agaricus, the sequence would have been: — White spores : 

 Russula, Lactarius, Hygrophorus, Nyctalis, Paxillus (Lepista), Cantha- 

 rellus, Marasmius, Lentinus, Panus, Xerotus, Schizophyllum, Lenzites. 

 Pink and brown spores : Bolbitius, Cortinarius, Paxillus (Tapinea). 

 Black spores : Gomphidius, Coprinus. It is singular that none of these 

 genera have purple spores, analogous with the Pratellec. So little 

 value does Fries attach to the colour of the spores amongst these 

 genera, that some of the species of his Paxillus have white spores, others 

 red. The genus Marasmius is so near the subgenus of Agaricus, Colly- 

 bia, that it is sometimes very difficult to determine to which group some 

 species belong. Fries himself is often very uncertain ; with some species 

 he has recently put the common Agaricus (Tricholoma) personatus, Fr., 

 into the genus Paxillus, partly on account of the gills separating from 



