798 



SCIENCE 



[N. S. Vol. XXXI. No. 803 



with the Fusarium. Through artificial culture 

 work it was found that 62.8 per cent, of the 

 tubers from a certain field was infected internally 

 with the Fusarium, along with which was also 

 the Vermicularia to an extent of 10.3 per cent. 

 Culture work upon beginning lesions in the stem 

 and roots usually brought out both of the fungi. 

 No experiments have been carried out to show 

 whether both these organisms are actually taking 

 part in the production of potato wilt, although 

 such experiments are now under way. 



On a Laboratory Method of Determining the 

 Fungicidal Value of a Spray Mixture or Solu- 

 tion: Dr. Donald Reddick and Mr. Ebbett 

 Wallace, New York State College of Agri- 

 culture. 



The method consists essentially of spraying 

 slides or cover -glasses with a spray substance of 

 a given formula. After proper drying and ex- 

 posure spores of the pathogen are placed on them 

 in a drop of meteoric water to germinate. This 

 method more nearly simulates natural conditions 

 than that of using a drop of the spray substance 

 direct. Experimental data in connection with the 

 conidia of Venturia incequalis have been obtained 

 which confirm the fact. 



Mycological Studies upon Wheat and Wheat Soils 



to Determine Possible Causes in Deterioration 



in Yield: Professor T. D. Beckwith, North 



Dakota Agricultural College and Experiment 



Station. (Read by Professor H. L. BoUey.) 



Analysis of soil solutions made from old wheat 



soil and from virgin prairie soil did not show 



siifficient differences to warrant the assumption 



that deterioration in yield is due to lack of plant 



food. 



Culture studies made from old wheat soil and 

 from virgin prairie soil show that certain soil 

 fungi belonging to genera known to be pathogenic 

 to some of the gramineae are present in the soil 

 cropped for years to wheat. They are almost 

 lacking in virgin soil, the probabilities being that 

 they are wind sown. 



These fungi belong to the genera Colleto- 

 trichum, Fusarium, Macrosporium. and Alternaria. 

 In order to ascertain whether spores of certain 

 of these fungi were normally to be found on wheat 

 stems a series of four hundred germination tests 

 were carried out by placing them in moist culture 

 tubes. Examination was made microscopically 

 after five days' incubation at 30° O. Following 

 are the results showing the percentages of wheat 

 infected by these fungi: 



"Nodes 



Golletotrichum 90.0 



Macrosporium 65.0 



Eelminthosporium 62.5 



Cephalotheoium 10.5 



Internodes 



CoUetotrichum 83.0 



Macrosporium 50.5 



Eelminthosporium 58.5 



Cephalotheoium 9.0 



This preliminary series showed the possibilities 

 for infection. The spores of these forms either 

 were resting on the wheat plants or else had 

 already germinated there. 



The next series consisted of another four hun- 

 dred nodes and internodes, but this time they 

 were sterilized by treating one minute with one 

 per cent, formaldehyde and afterward washing 

 with sterile distilled water. Thus it is presumed 

 that all saprophytes and surface fungi were eradi- 

 cated. These stems were then allowed to ger- 

 minate as in the former series. Microscopic ex- 

 amination showed the following per cent, infection 

 by the fungous genera given below: 



Nodes 



CoUetotrichum 57.0 



Macrosporium 53.5 



Eelminthosporium 40.5 



Fusarium 33.5 



Internodes 



CoUetotrichum 52.5 



Macrosporium 33.0 



Eelminthosporium 34.5 



Fusarium 27.5 



Finally culture experiments made from roots 

 of wheat grown in old wheat soil showed the 

 presence of CoUetotrichum, Fusarium and Macro- 

 sporium. 



These tests seem to prove ( 1 ) old wheat soil 

 is infected with certain fungi, (2) the spores or 

 mycelium of certain of these fungi are to be found 

 normally in or on the wheat plant grown on such 

 land, (3) a certain per cent, of the wheat is 

 pathologically infected with certain of these fungi, 

 (4) certain of these fungi cause root infection. 



Peach Yellows and Frost Injury: Mr. M. B. 



Waite, U. S. Department of Agriculture. 



(Read by C. L. Shear.) 



There seems to be some confusion about these 

 two troubles of the peach. It is the writer's 

 opinion that peach yellows has no relation what- 



