82 FUNGOID PESTS OF CULTIVATED PLANTS. 



and to that account we have nothing to add, heyond the intimation that 

 this disease partakes essentially of the characters of the well-known Potato 

 disease, and that whatever remedies may have been applied with success 

 in one instance are likely to avail in the other. 



The only fungicide which has been recommended for use in the early 

 stages of this disease is diluted Bordeaux mixture, but of course this will 

 be of no avail where the mould is well established and the mycelium has 

 penetrated deeply into the tissues of the host-plant so that the resting 

 spores are in course of formation. In such case the only alternative is to 

 prevent the spread of disease by destroying all affected plants which may 

 contain resting spores. 



Known through the whole of Europe, the greater part of America, 

 and in Asiatic Siberia. 



For development of " rot moulds " see Introduction, p. 2. 



Sacc. Syll. vii. 830 ; Mass. B. F. 119 ; Mass. PL Dis. p. 79 ; Smith, 

 Field Crops, 86 ; Gard. Chron. Nov. 17, 1883, figs. 109-111 ; Cooke, M. F. 

 f. 265 ; Cooke, Hdbh. No. 1778. 



Damping off. 

 Pythium De Baryanum (Hess.), PI. IX. fig. 99. 



This disease affects seedlings of Cress, Mustard, &c, when the plants 

 fall over and die oil', as a result of the destruction of the fundamental 

 tissues by the attack of this parasite. The stem fails just above the sur- 

 face of the ground. 



The mycelium is branched, with the lateral branches thin and reflexed. 

 The conidia are globose, with thin walls, often terminating the lateral 

 branches (20-30 p). The resting spores, or oospores, are also globose, 

 with a thick smooth outer coat (25-35 /i) resulting from the conjugation 

 of a club-shaped cell or antheridium with the globose cell which after- 

 wards becomes the resting spore (fig. 99 a). 



In many features of their life-history these fungi, called Ptjthium, 

 resemble the rot moulds, and especially in the production of zoospores. 

 The resting spores, however, are produced externally, and not within the 

 tissues of the host plant. 



This disease only occurs in very damp situations, and should be pre- 

 vented by i/ood drainage. 



Sacc. vii. <)2J ; Ward, Dis. p. 38, figs. 5-9 ; Mass. PL Dis. 54, fig. 4 ; 

 Quart. Journ. Micr. Sci. xxiii. p. 4<s7, t. 24, f. 1-10 ; Tubcuf, Dis. p. 116. 



Young Cabbage plants are often destroyed by Olpidium Brassica 

 when growing in damp places. The fungus is a single cell or two or 

 three, located in the cells of the host plant. From these imbedded cells 

 a tuhe is projected through the tissue so that the zoospores may escape. 

 Resting spores are formed within the substanco of the host-plant. 



Mass. PL Dis. 68. 



Cabbage Spbjbrella. 

 Sj>h,, \rella hmssic(ecola (Duby.), PL VII. fig. 100. 



This affection of the haves is hold to bo the mature condition of tho 

 leaf-spot, which occurs earlier in the year. The leaves are disfigured by 



