BOTRYTIS AS A PARASITE UPON CHRYSANTHEMUMS AND 



POINSETTIAS. * 



BY PERLEY SPAULDING. 



During the month of November, 1904, one of the smaller 

 greenhouses at the Missouri Botanical Garden was devoted 

 entirely to chrysanthemum plants which were just beginning 

 to come into bloom. Because of lack of room they were 

 badly crowded together, but especial pains were taken to 

 have the conditions as favorable as possible for the plants. 

 The taller ones, located in the middle of the house, came 

 into bloom first, and it was noted almost at once that the 

 flowers were affected by some disease which attacked the 

 petals. The trouble soon spread to the lower plants as they 

 came into bloom, and the disease was very shortly scattered 

 over the house. So far as observed, the trouble always first 

 appeared on the petals. The diseased flowers were picked 

 as soon as they were seen to be affected, so that the fungus 

 did not have a chance to infest the other portions of the 

 plants; for this reason it cannot be said that the fungus 

 might not have attacked other parts of the plants if it had 



' been left to run its course. 



d 



looking as if the petals had been pricked with a needle ; this, 

 of course, showed much plainer on the white flowers than 

 on the colored ones (pi. 32, above). These spots were gen- 

 erally more or less numerous on single heads, and even on 

 individual petals; they were often located only on one side 

 of the head, showing that the infection had come from 

 some point on that side of the plant. They very rap- 

 idly grew larger, and by the time the affected spot extended 

 over a fourth of the petal, the diseased tissues wilted and 

 dried up. Naturally the tips of the petals were first attacked, 



Agr 



(185) 



