DISEASES OF CULTIVATED PLANTS 637 



house is too moist, or if other conditions be slightly unfavorable, the 

 fungus seems to flourish all the better. It may be checked by the use 

 of Bordeaux mixture or by dilute copper sulfate solution, as recom- 

 mended for cucumbers in the greenhouse (One pound to fifty gal- 

 lons). (Ohio E. S. B. 214.) 



Nematodes. Among the most serious of the rose diseases is 

 that caused by the eelworms or nematodes which attack the roots. As 

 with cucumbers, these parasitic worms induce the growth of small 

 bead-like galls upon the roots of the rose. The leaves dry up from 

 the margins, the plants generally turning yellow and breaking down 

 as the outcome of this interference with the proper work of the roots. 

 No successful remedy has been found for plants once attacked. The 

 method of prevention consists, as in the case of cucumbers already 

 cited, in the proper steaming and treatment of the soil designed for 

 use in the rose benches. 



Rust ( Phragmidium subcorticium) . This is occasionally met 

 and proves very disfiguring. As yet we can advise nothing more 

 than the choice of rust resistant sorts. (Ohio E. S. B\ 214.) 



SNAPDRAGON. 



Anthracnose. It attacks the plants at any stage of their growth, 

 both in the greenhouse and in the field. In the greenhouse it is 

 more destructive in the fall and spring than during the winter. In 

 the field its ravages are most conspicuous in August and September. 

 On the stems it produces numerous elliptical sunken spots from 

 three to ten millimeters in length; and on the leaves circular dead 

 spots having a diameter of from three to five millimeters. These 

 spots are caused by an undescribed species of Colletotrichum for 

 which we here propose the name Colletotrichum antirrhini. Cut- 

 tings should be taken from healthy plants only. Anthracnose is 

 often transmitted from one generation of plants to the next by 

 means of infected cuttings. 



VIOLET. 



Spot Disease. This attacks the plants at any stage of their 

 growth from the small unrooted cutting in the cutting bed to the 

 mature plant in full flower. Plants that are making a vigorous, 

 rapid, but soft or succulent growth are most subject to the disease. 

 The disease may occur on any portion of the plant above ground, 

 but causes the greatest amount of loss when present upon the foliage. 

 Its first appearance upon the leaves is characterized by small, definite, 

 usually circular, greenish or yellowish white spots, resembling very 

 much the bite or sting of an insect. They vary in size from dots 

 scarcely perceptible to the unaided eye to spots a thirty-second of an 

 inch or more in diameter. The light-colored central portion or 

 point of infection is surrounded by a narrow ring of discolored tissue, 

 usually black or very dark brown at first, but changing to a lighter 

 shade as the spots grow older. As the spot develops the central por- 

 tion remains unchanged in appearance, while the tissues imme- 

 diately surrounding it, either to one side or more frequently in a 

 circle, become diseased by the ramifying growth of the mycelium 

 of the fungus through this portion of the leaf. This usually takes 



