130 PHYCOMYCETES. 



wet season is veij favourable to it. The mycelium is non- 

 septate and spreads through the intercellular spaces of the host, 

 nourished by button-like haustoria sunk into the host-cells. 

 The antheridium comes into contact with the oogonium by a 

 fertilization tube, wliich, however, remains closed. The oospores 

 hibernate in leaves and fruit. 



Prevention} Ammoniacal copper carbonate solution, eau 

 celeste, or Bordeaux mixture, prepared as described on p. 69, 

 may be used. The tirst-named solution seems least liable to 

 injure the foliage ; the others must, on this account, be used 

 with care. The first application is made about the time the 



Fii;. 41. — Plasmopara pygmaea on Anemone nemorosa. Conidiophores emerging 

 from a stoma. Intercellular mycelium with haustoria. (v. Tubeuf del.) 



berries are well formed, and the sprayings are repeated every 

 twelve to fifteen days, or oftener if there are heavy rains, till the 

 grapes begin to colour. It must, however, be remembered that 

 sprayings of this kind do not reach the mycelium inside the leaf, 

 but only act superficiall}^ killing any developing conidiophores 

 or conidia which may alight on the leaf. These fungicides are, 

 at the same time, remedies for powdery mildew (Uncinula). 



" Sulphuring" as a remedy for this aiid the powdery mildew 

 has been recommended by continental writers.^ The burning 

 of all diseased vine-leaves is strongly recommended. Attention 

 also sliould be given to the cultivation of disease-proof varieties.^ 



PI. pygmaea (Uiiger). On Rauuiiculaceae (Britain and U.S. Anuiiica). 

 PI. pusilla (De Bary). On Geraniums. 



Uialloway, "Fungous diseases of the grape and their treatment," U.S. 

 Dept. ofA</ric., farnierr Bulletin, No. 4, 1881. 



-Oesterr. Weinhaukongress, 1891. Reported in Oed. laudwirth. WochenhlaU, 

 X., 1881. 



•'MiUardet (see Chap, vi.) 



