NOMAO F'UNGl. 110 



thickened cutiole ; in Coleosporinm, mostly 4-celled and surrounded by 

 a tenacious gelatine. Gymuosporangiuni (with which Podisoma is 

 united) has for stage I. tlie various species of lla?stelia. Of Cronar- 

 tiuni, which has been discovered in Britain since the publication of the 

 Handbook.* only stages II. and III. are known. Peridennium is stated 

 to be the first stage tif Coleosporiuni, but concerning this it is, I think, 

 permissible to withhold one's opinion till further evidence is adduced. 

 Endophyllum is a curious genus, in which the spoi'es are produced in 

 chains, and surrounded by a pseudo-peridium, exactly as in CEcidiuni, 

 but nevertheless germinate like those of a Pucciuia, with the forma- 

 tion of a proniyceliunr and small round sporidia. It is found 

 embedded in the leaves of Kupliurbici (imyriduloidrs and species of 

 Sempervivum and Sedum. Dr. B. White has described (in " Scottish 

 Nat.," iv.. p. l()o) a new genus, Milesia, allied to Endophyllum, found 

 in the leaves of Pol i/ podium luilfidre. 



Of the genera included in the HauLlbook, which are not mentioned 

 in the foregoing list (p. 28), Xenodochus is absorbed in Phragmidium 

 (a change hardly to be recommended) ; Tilletia, Ustilago, Urocystis, 

 Thecaphora, and Tuburcinia are placed in the Ustilagiueae ; Cystopus 

 is removed to the Perouosporese ; Trichobasis is merely a synonym of 

 Uredo ; and Graphiola is not truly British. A number of species, 

 however, at present imperfectly known, must be arranged provision- 

 ally under the pseudo-genera Uredo, Cseoma, and fficidium ; such are 

 Uredo agrimoniie cuijatorue, U. lujdrocoUjles, U. quercuii, Ctcoma iiiercuria- 

 lis pereiinin, (Ecidiuiii qnadrijidum, (E. clematldis, and others, among 

 our British species. 



Meaning of the (Ecidium Stage. 



There is one point which strikes an attentive observer of the fore- 

 going phenomena very forcibly ; I mean, the apparent uselessness of 

 the oecidium-stage in the life-history of a Uredinous fungus. Why 

 should a puccinia-spore generate an Qicidium ? Why not produce the 

 Uredo at once ? Some Puccinias indeed have no Q3cidium, as P. malva- 

 cL'aruin, but why not all '? This is a question upon which I have seen 

 few attempts made to throw any light. We can see the object of the 

 Uredo and the Pucciuia, but not of the (Ecidium. There is only one 

 glimmer in the darkness, and that will be introduced by the point to 

 which I wish now to draw attention. I believe that in the life-history 

 of most plants there must occur, more or less frequently, a process 

 akin to the fertilisation of the phanerogams. There must be that 

 mysterious comniingling of the contents of two distinct cells, froin 

 which auimal and vegetable species alike derive a renewed lease of life. 

 Many facts point to the conclusion that a species which reproduces 

 itself only by budding has a tendency to degenerate continually, and 

 finally to become extinct. It is true that there are apparent (or real) 

 exceptions to this law, where a species maintains itself, so far as we 



* See " Grevillea," iii., p. 124. 



