PEACH SCAB AND ITS CONTROL. 37 



could be seen to sway, but the spores remained in place. When a drop of water was 

 brought in contact with the spores, however, they quickly became detached. 



Experiment 4- — An abundantly sporulating culture on a section of a steamed bean 

 pod was placed in a glass tube, 2 cm. in diameter and 30 cm. long, about 2 cm. from the 

 distal end, in such fashion that no part of the colony touched the glass. A glass slide 

 smeared with glycerin was placed about 1 cm. from the opening of the distal end of 

 the tube in position to catch particles which might be blown through. For about 30 

 seconds a strong current of air was aspirated into the proximal end of the tube by 

 means of a hand bellows. While no attempt was made to measure the velocity of the 

 air current, it was strong enough to move the section of wet bean pod several milli- 

 meters. It was thought to be at least the equivalent of the strongest wind ordinarily 

 affecting an orchard. Subsequent careful microscopic examination of the slide showed 

 that only occasional spores were present. In most of these cases the conidiophores, 

 rather than the spores, had been detached. 



Experiment 5. — The culture used in the preceding experiment was gently sprayed 

 with distilled water by means of an atomizer, in such fashion that only the finest par- 

 ticles of spray fell upon it. When a drop of water accumulated at the bottom of the 

 pod it was examined microscopically and found to contain myriads of conidia. 



Experiments 6 and 7 . — Experiments 4 and 5 were repeated, with confirmatory results. 



Experiment 8. — On April 23, 1915, a peach twig about 10 cm. long, similar to those 

 used in experiment 2 and bearing more than 30 abundantly sporulating scab lesions, 

 was clamped about the base by a cork which was inserted in a bottle of water. Thus, 

 the twig was kept fresh and turgid, with about 7 cm. of its length exposed. In this 

 condition it was placed out of doors in a brisk wind for two hours. A glass slide 

 smeared with glycerin was placed 1 cm. away from the twig upon the leeward side, 

 in position to catch spores which might be blown off. At the end of the experiment 

 a careful microscopic examination of the slide revealed only occasional spores of 

 Cladosporium carpophilum. 



Experiment 9. — The twig used in the preceding experiment was placed in the aspi- 

 rating apparatus employed in experiment 4, in such position that it did not touch the 

 surface of the tube. The aspirator was operated as in experiment 4. Only occasional 

 spores could be found upon the glycerined slide, though they were slightly more 

 abundant than in the preceding test. 



Experiment 10. — The twig used in the preceding test was sprayed in the manner 

 described in experiment 5. The drops of water which accumulated contained myri- 

 ads of conidia. 



Experiment 11. — The twig used in the preceding test was allowed to dry over night 

 in the laboratory. The next day it was put in the aspirating apparatus and treated as 

 in experiment 9. The results were not materially different from those of experiment 

 9, though the number of conidia caught was very slightly increased. 



Experiments 12 to 15. — Experiments 8 to 11 were repeated, with confirmatory results. 



The results of these and of other similar experiments show: (1) 

 That the dry conidia of Cladosporium carpophilum are not normally 

 abscised or abjected; (2) that in a dry or hmnid atmosphere they 

 remain persistently attached to the parent fungus; (3) that in con- 

 tact with water they promptly become detached; (4) that even after 

 spores have been detached by wetting the twigs they are not readily 

 disseminated by wind after a period of drying. Thus, the evidence 

 strongly indicates that under orchard conditions wind may be ex- 

 pected to play only a minor role in the dissemination of conidia, while 



