350 Bulletin 163. 



a very violent kind, but that it may cause damping off of lettuce, 

 cotton, and some other plants to a limited extent. Owing to the 

 similarity in morphological characters of these forms of Rhizodonia 

 from the sources mentioned, and with the experimental evidence 

 available, it seemed at first that these forms were exactly identi- 

 cal. Further evidence ma}' indicate that we must recognize 

 differences which are at least racial, not permitting of the ready 

 transfer in a single generation of the beet fungus to seedlings of 

 other Dlants, or vice versa.* 



Mr. F. C. Stewart, of the Geneva Station, is at work upon a 

 stem rot of carnations and the fungus causing this disease of 

 carnations is identical in all morphological characters with the 

 Rhizodonia of beet root-rot. Experimental proof has also been 

 established showing that the two diseases are due to the same 

 organism ; and this evidence is detailed in the paper mentioned 

 below. 



From the work of Kiihn and Pammel it is quite evident that 

 the beet fungus should be referred to Rhizodonia Betoe Kiihn ; 

 but at this time it is undesirable to enter into any discussion con- 

 cerning the proper limitation of species in this genus w^hich has 

 been variously treated by Tulsanef, ComesJ, and others. 



f. Remedies. 



The use of lime as a possible preventive for certain 

 rhizoctonial diseases has been recommended. The use 

 of an alkali as a preventive might be logically suggested 

 knowing the avidit}' with which the fungus grows on acidulated 

 nutrient media. The failure of the Rhizodo7iia to cause trouble 

 in those parts of the field where coal ashes had been used abun- 

 dantly again suggests the same remedy. Furthermore, Mr. F. C. 

 Stewart has determined that a small amount of alkalinity is fatal 



* Further details bearing upon the similarity of these forms of Rhizoc- 

 tonia will be found in a paper presented before the Society of Vegetable 

 Morphology and Physiology, Dec, 1898, entitled "Different Types of Plant 

 Diseases Due to a Common Rhizodonia,'' by B. M. Duggar and F. C. Stewart. 

 This paper will soon be published in the Botanical Gazette. 



f Tulasne, L. R- & C. Fungi Hypogsei, pp. 188 — 195. 



X Comes, O. Crittogamia Agraria. 



