Bean Anthracxose 145 



the seedlings. The plants, being larger, are more likely to be in contact 

 with one another and thus make easier the transmission of the spores. 

 If the vines have a tendency to hang low and be bushy, the air beneath 

 thern remains sufficiently humid for spore germination for a longer time 

 after rains and dews than does the air outside. During rains the drops 

 of water on the plant run together and move over the surface, in some 

 places dripping from the leaf apices to other leaves and vines, in other 

 places running down the stem or falling in large drops on the pods, where 

 they spread out over the surface as they strike. When wind accompanies a 

 storm, the wet leaves are blown against one another, against the leaves 

 and stems of other plants, or to the ground. If a plant is affected with 

 anthracnose, multitudinous spores from the various lesions become 

 suspended in the rain water and are carried as described to the healthy 

 parts of the plant. The pods become inoculated in this manner and in 

 other ways. 



When falling raindrops strike a spore-producing lesion or a film of 

 water anywhere containing spores, drops of the contaminated water are 

 spattered to the near-by stems and leaves. Faulwetter (1917), in his 

 efforts to explain the rapid dissemination of Bacterium malvacearum, 

 has made some interesting experiments to determine the distance to 

 which water can be splashed by falling drops of various sizes. He finds 

 that splashing occurs only when drops fall on a film of water, and that 

 it is the water of the film that is splashed. A drop 0.1 cubic centimeter 

 in volume falling 16 feet onto a film over a glass plate spattered water 

 as far as 64 inches. A drop 0.02 cubic centimeter in volume falling 16 

 feet during a wind of 10 miles an hour "splashed water in abundance a 



distance of 8 feet in moderate quantities as far as 12 feet and 



in slight amounts to 16 feet." He concludes that the possibilities of 

 dissemination of bacteria in suspension in film water on cotton leaves 

 " are considerable if one includes the distance bacteria may be carried 

 from the original lesion, then splashed up again and carried farther, and 

 so on, until a dilution too great for infection is obtained." 



In addition to being splashed from contact with falling raindrops, 

 contaminated drops of water may be carried bodily during a heavy wind 

 to healthy parts of the plant, and plants blowing against one another 

 will aid in disseminating the spores. Persons, as well as dogs, rabbits, 



