FUNGI IMPERFECTI 329 



The fungus produces black spots on stems and petioles, very 

 rarely on the leaves. It is stated that the plants seem to suffer the 

 greatest injury, first, when the seedlings encounter prolonged dry 

 weather ; and again, during the ripening of the seed, when the 

 effects are more severe on the stems just above the surface of the 

 ground. The conidia are hyaline, generally straight and rounded, 

 11-13 x 3-4/4. The setae are continuous or I -septate, fuliginous, 

 apex pale, 39-62 x 4-7 /4, often sinuous or nodulose. It is improba- 

 ble that any cultural methods would be effective in preventing the 

 spread of this disease. Selection of seed from apparently resistant 

 plants have yielded offspring which likewise developed the disease 

 to less extent. It remains, however, to be seen if this may not be 

 due in part to clean seed selection. 



XXX. ANTHRACNOSE OF SNAPDRAGON 



Colletotrichum Antirrhini Stewart 



STEWART, F. C. An Anthracnose and a Stem Rot of the Cultivated Snap- 

 dragon. N. Y. Agl. Exp. Sta. 179: 105-109. 1900. 



The above fungus is, according to Stewart, the most serious 

 disease of the snapdragon (Antirrhinum majus], as cultivated in 

 greenhouses in the United States. It is also destructive in the 

 garden. In greenhouses the greatest injury occurs generally in the 

 spring and fall, and in the open during late summer. It attacks 

 both stems and leaves at practically any stage of growth. 



On the leaves circular dead spots are produced, and on the 

 stems elliptical sunken areas 3-10 mm. in length. The spots on 

 the stems frequently become confluent, and girdling may some- 

 times result. 



Small dark stromata are produced in the centers of these spots, 

 each under favorable conditions becoming an acervulus by produc- 

 ing short conidiophores bearing straight or slightly curved conidia, 

 1 6-2 1 x 4/4, and also several dark, tapering setae, 50-100/4 long. 



Cuttings should be made from healthy plants only, and over- 

 head watering avoided when possible. If it is necessary to spray 

 young plants, Bordeaux mixture is effective ; but a fungicide which 

 does not discolor the foliage should be substituted if further treat- 

 ments are required. 



