.I50 



Journal of Agricultural Research 



Vol. XVI. No. s 



DISSEMINATION 



This fungus, as is the case v^^ith many others, is no doubt disseminated 

 in numerous ways. After the infected plants are mature the sporangia 

 are Hberated in large quantities and are free to be carried by such agen- 

 cies as wind, running water, insects, and various animals, including man. 



Wind is certainly responsible for considerable dissemination of spo- 

 rangia. This was demonstrated, as will be shown by Tables I and II. 

 Table I shows the results of sporangium catches on common microscopic 

 slides at Agricultural College, Miss., in January, 1918. These slides were 

 coated on one side with ordinary vaseline (a method used by l^.Ir. H. D. 

 Barker, of this Office, for catching wind-blown spores) and were placed 

 on stakes i inch square at heights of i, 2, and 3 feet. A slide was placed 

 on each of the four sides of the stake at the different heights and held in 

 place by rubber bands passing around each end of the four slides and 

 the stake. The stakes were placed in the field so that the slides were 

 facing the four points of the compass. A larger number of spores were 

 caught on the slides facing the prevailing winds at the time the experi- 

 ment was conducted. The slides were brought into the laboratory and 

 marked off crosswise in narrow strips by running a sharp pencil through 

 the vaseline. These lines ser^^ed as guides while counting the spores 

 with a microscope. 



Table I. — Catches of -wind-blown sporangia of Physoderma zeae-maydis at Agricultural 

 College, Miss., in January, igiS 



o stake 3 was blown down during the experiment. 



