84 The Scottish Naturalist. 



becoming dark in glycerine. Oospores (described by 

 De Bary as yellow-brown, covered with a wide-meshed 

 network of thick ridges) not observed in Scotland. 

 The affected leaves bear the conidiophores only on the 

 lower surface ; on the upper surface they become 

 yellowish-green and then brown. 



P. obovata Bon., spreading uniformly along stems and leaves 

 in a greyish coat of conidiophores, which are 200-220 

 long, are 5-6 times bifurcated, and end in short, rather 

 rigid, spreading or slightly recurved branchlets ; conidia 

 obovate, 24 by 12-13 (Schroeter gives 24-38 by 15-18), 

 violaceous. Oospores, (found in plants that did not 

 show conidiophores), globular, 30-40 diam., brown, with 

 an irregular network of ridges, much like oospore of P. 

 Ahinearum. 



P. Potentillae De Bary j var. Gei Trail (off Geum riva/e, near 

 Aberdeen). Conidiophores (covering patches on lower 

 surface of leaves, rendering them grey), 220 long, 

 rather slender, six times bifurcated, ending in short re- 

 curved branchlets. Conidia dark violet, ellipsoid, 12-13 

 by 10-12. Schroeter gives conidia of P. Potentillcb as 

 20-24 by 16-18, and says that oospore has clear brown 

 smooth epispore. 



P. Chrysosplenii Fuckel. Conidiophores rather wide apart, 

 over lower surface of leaf, white ; five to seven times 

 bifurcated ; Conidia ovate, 20-22 by 15-18. Oospores 

 (globular, 28-30, clear brown, wall thick, often with an 

 indistinct network of ridges) not observed in Scotland. 



P. Scleranthi Rabh. The conidiophores and conidia are 

 scarcely distinguishable from those of P. Alsinearum, of 

 which this is probably a mere form. 



APPENDIX II. 



It is probable that some or other of the following Peronosporete 

 will be found in Scotland if looked for carefully, since 

 all occur in Germany, and some of them in England. 

 Phytophtbora Cactorum L. and C. On various plants, 

 Beech seedlings, &c. 



Peronospora (Plasmopara; pusilla De Bary, on leaves of 



Geranium pratense, G. phaeum, and G. sylvaticum. 



