1891.] PUBLIC DOCUMENT — No. 33. 221 



some stages in the production of resting spores. Other 

 resting bodies (gemma) may be formed from the threads in 

 a purely vegetative way (Fig. 22). 



The very general distribution of this fungus is indicated 

 by the fact that the soil in which the affected seedlings grew 

 in the present case was, as nearly as possible, virgin soil, 

 having just been brought from a natural woodland, where 

 it had probably been undisturbed for a very long period, 

 into a new greenhouse then first used. 



Assuming that " damping off" is always caused by the 

 same fungus, certain directions for its treatment may be 

 given. Plants affected should be at once removed, with 

 the soil immediately surrounding them, and burned. If 

 this is done as soon as the seedling falls, the trouble can 

 be held in check, since the fungus will be destroyed before 

 its reproductive organs have developed. When a hot-bed 

 or propagating bench has become so badly infested by the 

 fungus that a large part of the seedlings or cuttings " damp 

 off," the soil should be entirely removed to a distance, and 

 the containing walls thoroughly cleaned and washed with 

 strong whitewash, and refilled with fresh earth. After 

 this treatment, the prompt removal of diseased plants 

 should be sufficient to limit the trouble to an occasional 

 case. 



The Mildew of Spinach (Pcronosfora effusa (Grev.) 

 Rabh.) caused serious damage to that crop on the grounds 

 of the Massachusetts Agricultural College. This fungus 

 is one of the downy mildews, and makes its presence 

 known by the appearance of discolored blotches on the 

 upper surface of the leaf, and corresponding patches of its 

 closely matted spore-bearing threads on the lower surface. 

 Since this crop is cultivated for the leaves, the disease 

 should be controlled by picking and destroying the leaves 

 as fast as they become attacked, and by thorough cleaning 

 of the field as soon as the crop is removed. 



Spinach belongs to the same family of plants with some 

 of our common weeds, which are also attacked by this 

 mildew. One of these which appears in almost every field 

 is the so-called pigweed or lamb's quarters ( Chenof odium 

 album). This plant is equally subject to the attack of the 



