1890.] PUBLIC DOCUMENT — No. 33. 229 



report, in December, 1888. The leaves showed the dark, 

 cloudy and dendritic patches, and the small, slightly raised 

 pustules characteristic of the " black spot" of the rose ; and 

 the microscope showed the presence of an abundant mycelium 

 in the spots, producing at certain points masses of the spores 

 of the "black-spot" fungus, A.ctinonema rosoe Fr. The 

 spore-bearing spots are indicated by the pustules, which are 

 formed by the elevation of the surface layer or epidermis of 

 the leaf by the developing spore masses. As the internal 

 tissue of the leaf is invaded by the mycelium, it is gradually 

 killed, and loses its green color; so arise the- discolored 

 spots, which give the disease its name, and which, at first 

 small, spread radially in all directions from the point of 

 infection. The fungus which causes this trouble is one of 

 the imperfect fungi, and its relation to other forms remains 

 still undetermined. 



The same disease appeared abundantly on leaves of roses 

 cultivated out of doors in the garden of a very successful 

 amateur in Amherst, last summer. 



Infected leaves should be carefully collected and destroyed, 

 to prevent the dissemination of spores ; and it is probable 

 that spraying with some fungicide will prove etficacious in 

 checking the disease, if done early and frequently enough. 

 For fuller details and recommendations, reference may be 

 had to the report of the mycologist of the United States 

 Department of Agriculture, for 1887, p. 366, and to Bulletin 

 No. 6 of the Hatch Experiment Station, before referred to. 



3. Nematode Disease of Oucwmbers. — A disease seri- 

 ously affecting cucumbers raised under glass came to my 

 attention in July last, through Mr. H. T. Fernald of 

 Amherst. It manifests itself first in the yellowing of the 

 foliage, which is followed by the death of the plant. But 

 the real seat of trouble is in the roots, on which are formed 

 rough, tubercle-like swellings or galls, in which the tissues are 

 loose and spongy, and easily crumble. Examination showed 

 the presence in these galls of very numerous microscopic 

 worms and their eggs. The worms measure perhaps one- 

 fiftieth of an inch in length, and belong to the group known 

 as thread-worms or nematodes, which attack the roots of 

 many plants with fatal results. 



