378 



SCIENCE. 



[N. S. Vol. I. No. 14. 



prevail, the spread of this pest has been 

 phenomenal. From a siagie center in South 

 Dakota, where it was brought in flax seed 

 from Eussia a few years ago, it has been 

 disseminated in all directions, so that to-day 

 it may be expected in almost any State in 

 the Union. Its spread is not confined to 

 to its natural methods, for with our lines 

 of railway running in all directions the 

 seeds are carried rapidly and for long dis- 

 tances. 



As an outcome of the advent of the Rus- 

 sian thistle, there has been a wide and 

 thorough awakening upon the subject of 

 weeds wliich will result in a better under- 

 standing of these foes, their ways of migra- 

 tion to and throughout our country, and the 

 best methods of subduing them. 



THE BEET-LEAF SPOT AND ITS REMEDIES. 



The last Bulletin (ISTo. 107) of the New 

 Jersey Experiment Station describes a fun- 

 gous trouble of beets in the United States, 

 the Cercospora beticola, Sacc, which causes a 

 conspicuous spotting of the foliage. There 

 seems to be no respect shown for any vari- 

 eties of beets, for the writer has made special 

 visits to the trial grounds of large seed- 

 growers, and all sorts of beets, from the 

 oldest to the newest kinds, were found with 

 their foliage about equally injured. 



The common name of ' Leaf Spot ' well 

 describes the general appearance of the beet 

 leaves infested with this Cercospora, for 

 they are at first more or less covered with 

 small light or ashy spots, which later often 

 become holes by the disappearance of the 

 tissue previously killed bj^ the fungus. 

 Figure 1 is an engraving made from a sun 

 print of a beet leaf, natural size, that was 

 badly infested with the Cercospora. Full- 

 sized leaves often become mutilated, and 

 sometimes scarcely more than the frame- 

 work remains. The fungus itself is quite 

 similar in structure and habits of growth to 

 those causing leaf spots and blights in other 



crops. The so-called ' rust ' of celery is due 

 to a Cercospora (Cercospora Ajni Fr.), as 

 likewise is the violet leaf spot (Cercospora 

 Viohe Sacc. ) . These fungi consist of slender 

 threads wliich run through the substance of 

 the leaf, and, coming to the surface in 

 groups, pass through the openings (stomata) 

 in the skin, and in clusters bear long, slender 

 spores in considerable numbers. These 

 spores, when mature, fall from their points 

 of attachment and soon germinate, thus 

 spreading the fungus and causuig other 

 spots. 



During the past season, under the special 

 charge of Mr. J. A. Kelsey, spraying exper- 

 iments have been carried out to check the 

 Cercospora of the beet. A field of Man- 

 golds, kindly provided by Supt. E. A. Jones, 

 at the College Farm, was experimented 

 upon with Bordeaux mixture. 



As the season progressed the Bordeaux 



