New York Agricultural Experiment Btatiox. 413 



While it is undoubtedlj true that the germ robs its host of a 

 great deal of nourishment, the death of the host-plant seems to 

 be due, chiefly, to the cutting off of the water supply. This view 

 is supported by the fact that in dry weather plants growing in 

 moist situations suffer less from the disease than plants growing 

 in drier situations; and while plants may die from the disease 

 in wet weather it is most virulent in dry weather. If plants are 

 examined in periods of wet weather it will be found that the 

 amount of the yellow substance which they may contain in their 

 vessels without showing outward symptoms of the disease is 

 much greater than it is in dry weather. Ordinarily, it is not easy 

 to detect the germ in plants which show no outward symptoms, 

 either by wilted leaves or dwarfed size; but in very wet weather 

 plants seemingly in perfect health will be found to contain a 

 considerable quantity of the germ. It is interesting to observe 

 the effect of alternating periods of wet and dry weather. For 

 about one month preceding July 12, 1897, it was very dry on 

 Long Island — so dry that in the latter part of the period some 

 crops suffered severely. During this time the corn disease was 

 very destructive. Then came about three weeks of rainy weather 

 followed by a short period of dry weather. Many plants which 

 were partially dead revived during the rainy season and prom- 

 ised to outgrow the disease, but as soon as the rains ceased they 

 suddenly collapsed. 



The vessels, which constitute the chief avenue for the ascent of 

 water, are so thoroughly plugged with millions upon millions of 

 bacteria that it is indeed no wonder that the plant dies from lack 

 of water. A good idea of the immense numbers of bacteria 

 which throng the vessels may be obtained by examining Plate 

 XVII, which is a photomicrograph of a longitudinal section of a 

 diseased corn stem. The bacteria swarm out of the ends of the 

 vessels like smoke out of a chimney. In cross-section (See Plate 

 XVIII), they ooze out in such numbers as to obscure the structure 

 of the fibro-vascular bundles. 



The germ seems to have no power to pass through the walls of 

 the parenchyma cells. This was especially noticeable in field 

 corn and pop corn plants artificially inoculated by puncture. The 

 germ was to be found only in the bundles which had been rup- 



