i8o Journal of Agricultural Research voi. xviii. no. 4 



He did not describe nor illustrate the disease on leaves, however; and 

 although the spots on pods and stems, as shown in his plates, do not 

 seem to be characteristically different in type from the lesions caused by 

 the organism discussed in this paper, his report on cultural and morpho- 

 logical studies precludes the possibility of the two organisms being the 

 same. 



APPEARANCE OF THE DISEASE 



On the leaves, where the disease is very conspicuous, the blight is 

 characterized by small, angular lesions. When young these spots are 

 translucent and water-soaked in appearance and yellow or light brown 

 in color; when old they are dark reddish brown to almost black, very 

 little of the translucency remaining. Single spots are usually from i 

 to 2 mm. in diameter and may be quite generally scattered over the leaf 

 surface, although they are often thickly grouped and confluent, resulting 

 in irregular lesions several millimeters in diameter or even so large as to 

 involve considerable portions of the leaf. Frequently, also, the spots 

 seem to take the course of the principal leaf veins, and marginal infec- 

 tions are not unusual. Very often a yellowing of the tissue surrounding 

 the lesion occurs. In advanced stages the invaded tissues may become 

 dry and fall out, thereby giving the leaf a very ragged appearance (PI. A). 



Evidence all points strongly to the fact that the bacterial blight of 

 soybean is not confined to leaves alone but that it affects also the stems, 

 petioles, and pods. Black lesions on the stems and petioles, varying in 

 size from very small spots to those of considerable length and breadth, 

 are often found accompanying the trouble on the leaves, and water- 

 soaked spots from which drops of exudate were oozing have also been 

 found on young petioles (PI. 12, A). 



On the pods the disease appears first as small water-soaked spots, 

 often showing exudate droplets (PI. 12, B, C). The lesions may grow 

 much larger, sometimes involving a considerable part of the pod. They 

 usually turn to dark brown or black with age, the exudate drops fre- 

 quently drying down as brownish nubs or scales. The seeds within dis- 

 eased pods also become affected and may be found covered with a slimy 

 bacterial growth (Pi. 13, A, B). 



Isolations made from petioles and pods such as are here described 

 have produced typical lesions when applied to soybean leaves, and 

 re-isolations have yielded the typical organism. 



Under the lens or even with the unaided eye, glistening exudate may 

 often be observed in small quantities on the underside of the leaf spots. 

 This ooze seldom appears as droplets in the field, except under very 

 favorable moisture conditions, but infected tissue allowed to remain 

 in a damp chamber for a number of hours is often covered with tiny 

 drops of the grayish white exudate. These, however, on exposure to 

 the air, dry very readily as inconspicuous brownish granules or scales, 

 or seem to disappear entirely. 



