7 8 The Scottish Naturalist. 



The family selected for revision in the following paper is one of 

 the most interesting, on account of the parasitic habits of the fungi* 

 and of the harm inflicted byseveral of thespecies oncultivated plants. 

 It is moreover very well defined by the peculiarities of its sexual re- 

 production ; and the genera met with in Britain differ sufficiently 

 from one another to render their recognition not a difficult task. 

 Moreover the classification followed in the Mvcolo^ia Scotica 

 separates the genera of this family widely from one another, 

 placing Cystopus with the family of Uredinece, and Peronospora 

 among the Hypkomycetes, groups with which neither is closely 

 allied. Under Peronosopora also are included three species, 

 different from it in their true nature ; these will be pointed out 

 below. In addition to these reasons for selecting the Peronosporece 

 for revision, several species new to Scotland have been added 

 within the past two years, and a number of those previously 

 recorded have been discovered of late years on foodplants and in 

 localities from which they were previously unknown in Scotland. 



In giving the districts in which the fungi have been detected, I 

 have for brevity, made use of numbers instead of the names 

 employed in the Mycologia and its supplements ; but the districts 

 themselves are the same, except in the sub-division of " Moray " 

 into two. The correspondence of the numbers and districts is as 

 follows : i Tweed, 2 Solway, 3 Forth, 4 Clyde, 5 Tay, 6 Argyle, 

 7 Dee, 8 Moray south of the Caledonian Canal, 9 Moray north 

 of the Canal, 10 West-Ross, 11 Sutherland, 12 Caithness, 13 

 Outer Hebrides, 14 Orkney, 15 Shetland. 



In the subjoined notes, all records of districts and of food- 

 plants not previously given in Mr. Stevenson's book, are printed 

 in italics. 



At the end of the list will be found, I, names of the species 

 wrongly included in Peronospora-, II, brief descriptions of those 

 species not described in Cooke's Handbook of British Pungi\ or in 

 the works mentioned above ; and II T, a list of species 

 of Peronosporea?, several of which should occur in Scotland, with 

 the names of their foodplants. It is hoped that this list will prove 

 useful to students of Scottish fungi, and that it will assist in the 

 extension of our knowledge of these parasites. 



Pythium Prings. 

 P. de Baryanum Hesse, 7, in dead Equisetum limosum, near 

 Aberdeen, plentiful. 



