xxv.] CORN MILDEW AND BARBERRY BLIGHT. 193 



we are inclined to look upon the upper and first-produced 

 dark cell as female, and the lower, often smaller, and 

 more transparent cell as possibly sometimes male. It is 

 known that the lower cell is from the first often smaller 

 and much more transparent than the upper one. It is 

 the upper one that usually produces pro -mycelium. 

 When both cells produce pro -mycelium, as they fre- 

 quently do, both are female. We believe it to be possible 

 that impregnation from a male element is not necessary 

 for every generation, but that fertile female spores may be 

 produced for several generations without impregnation 

 from a male organism. A comparable case of involved 

 sexuality occurs amongst molluscs. Many land snails are 

 monoscious that is, each individual is male and female 

 in itself, and capable of fertilising itself. The character 

 varies in different genera. In the Valvatidce the indi- 

 viduals which are at first male ultimately become female. 

 A similar phenomenon may possibly hold good in Puccinia 

 and its allied genera. A comparable phenomenon is 

 common and well known in plant-lice or Aphides. Mr. 

 G. B. Buckton, F.R.S., writes that in some instances 

 " males occur only at such remote intervals that their 

 action seems to exist at a minimum." 



We do not say that the involved changes advanced by 

 some botanists are impossible in the life-history of a single 

 fungus, but we have shown that they are unnecessary, as 

 Puccinia Rubigo-vera, D.C., can apparently reproduce 

 itself for an indefinite period of time in Europe without 

 an dEcidium condition ; Puccinia graminis, Pers., can do the 

 same in Australia ; the allied Podisoma Juniperi-Sabince, 

 Fr., does so in America. Chrysomyxa Ledi does so in 

 Greenland, and Puccinia obscura, Sch., in America, where 

 the daisy, on which its supposed alternate form is said to 

 grow, is not found in a wild state. 



To us the pro-mycelium, pro-mycelium spores, and 

 sporidioles, potential in Puccinia and ^Ecidium alike, tell 

 strongly against the idea of the genetic connection of the 

 



