1895.] MICROSCOPICAL JOURNAL. 145 



But to say that the diatoms increase slowly and regu- 

 larly does not tell the whole story. Oftentimes they de- 

 velop with extraordinary rapidity, sometimes jumping 

 from 132 to 1,575 per c. c. in a single week, as Asterio- 

 nella did in Walden Pond, Lynn, Mass., in October, 1893. 

 The reason for these sudden and enormous developments 

 is not known. We have tried to associate them with 

 some sudden increase in the amount of food material. 

 But though we have been thus far unsuccessful, it is quite 

 probable that that is the cause. It is possible, as some 

 have suggested, that it is in some way connected with 

 the formation of sporangial frustules, the result of con- 

 jugation. 



Bacteriosis of Rutabaga. 



{Bacillus campestris n. sp.) 



By L. H. P/^MMEL, 

 AMES, IOWA. 



During the month of August, 1892, my attention was 

 called to a disease of rutabagas, which, at that time, had 

 consumed more than ten per cent of the crop. The dis- 

 ease was spreading rapidly, owing to the favorable con- 

 ditions of the weather, warmth and moisture. The ground 

 was very moist, owing to frequent rains in July and early 

 August. The disease became so severe that in some pat- 

 ches, by the middle of September, more than half of the 

 crop was destroyed ; it was equally disastrous to some 

 yellow turnips. 



In 1893, the disease was again severe to rutabagas ; in 

 one case more than fifty per cent were destroyed. A 

 special student, Mr. J. A. Rolfs, who examined a large 

 number of rutabagas for me, makes the following report 

 on the extent of the injury : 



"On September 3d I examined the rutabagas east of 



