FUNGOID PESTS OF CULTIVATED PLANTS. 247 



CLOVER BLACK MOULD. 

 Polythrincium trifolii (Kunze), PI. XXIV. fig. 39. 



This black mould is not at all uncommon on the under surface of 

 living Clover leaves, and has the credit of being the imperfect condition of 

 some more highly organised fungus, possibly of Phyllachora Trifolii. 



The clusters are convex and cushion- like, with a powdery appearance, 

 and of a dark olive-brown, almost black colour, often seated upon yellowish 

 spots. The threads are erect, collected in bundles, flexuous and beaded, or 

 shortly jointed and constricted at each joint, thickened upwards, blackish 

 in the mass. The conidia are obovate, or rather narrowed downwards, 

 and divided transversely into two cells (20-24 x 9-12/u), pale olive ID 

 colour. 



Eeported in France, Germany, Finland, Bohemia, Italy, Asiatic 

 Siberia, and North America. 



Probably would be dispersed by spraying with dilute Bordeaux 

 mixture. 



Sacc. Syll. iv. 1664 ; Cooke, Hdbk. No. 1748 ; Grev. Sc. Crypt. Fl. 

 pi. 216. 



CLOVER-LEAF BLOTCH. 

 Phyllachora Trifolii (Pers.), PL XXIV. fig. 40. 



This is not an uncommon parasite on the leaves of Trifolium repens, 

 and may be the more perfect condition of the Clover black mould, but 

 this is not determined. 



It occurs on the under surface, forming oval or elongated, small, 

 shining, black, pitchy-looking convex blotches. These stroma, or pustules, 

 enclose one or more cells with whitish contents. When mature these 

 contain club-shaped sacs or asci, packed side by side, each of which 

 encloses eight elliptical colourless sporidia. 



The fungus is recorded for Sweden, Finland, France, Germany, 

 Italy, Asiatic Siberia, and North America. 



It is doubtful whether spraying would have any beneficial effect. 



Sacc. Syll. ii. 5184 ; Cooke, Hdbk. No. 2416. 



CLOVER-ROT MOULD. 

 Peronospora Trifoliorum (De Bary), PL XXIV. fig. 41. 



The Clover-rot mould attacks numerous plants, but especially Tri- 

 folium, Lotus, Medicago, and Melilotus, covering the entire under surface 

 of the leaves with a delicate greyish film. The fertile threads are six or 

 seven times forked, or sometimes trifurcate, and the ultimate branchlets are 

 pointed and slightly curved. The conidia are elliptical, obtuse, and of a 

 faint, dirty-lilac colour (18-27 x 15-20/z). The resting spores are 

 globose and brown, with a smooth surface (25-88/t). 



It is unnecessary to repeat here the details, which will be found 

 recorded in the "Introduction," of the modes of reproduction and 

 distribution of the rot-moulds, and the formation of the resting spores. 



