EXPERIMENT STATION BULLETINS. 663 



was little or no transpiration from the diseased spots, indicating that 

 with complete desiccation and shrinkage, the spots are cut off from the 

 water supply. 



Of the three possibilities outlined on page 34, the experiment points 

 to the second case where the diseased areas transpire more and the 

 healthy portions of the leaflets less, but the writer is fully aware of the 

 meagreness of his data. 



IMMUNITY PHENOMENA. 



Cross Inoculations: 



The following plants related to the tomato were inoculated by plac- 

 ing a loopful of spore suspension from a pure culture on various leaf- 

 lets.^^ 



Solanum quinescens 

 Capsicum frutescens 

 Nicotiana tabacum (tobacco) 

 Solanum tuberosum (potato) 

 Solanum villosum 



Within five days the potatoes showed definite small black spots on all 

 the inoculated leaflets, while the check leaflets showed no infection. None 

 of the other plants showed any spots. 



The experiment was repeated with the same results. Various attempts 

 to find pycnidia in the infected areas of the inoculated potato leaves 

 have failed in these preliminary experiments. This is a most interest- 

 ing result inasmuch as no Septoria has been described upon potato 

 (Saccardo). It is also hard to explain the absence of such a record in 

 view of the frequent association of tomatoes and potatoes in the field, 

 unless the failure to produce pycnidia is a uniform condition. More ex- 

 tensive experiments are planned. At present, it is important to note 

 that these spots were obtained by merely applying the spores, not injur- 

 ing the tissue in any way. The importance of further investigation upon 

 this point is obvious. 



Susceptibility of Varieties: 



The following varieties Avere obtained from D. M. Ferry & Co., Detroit, 

 Mich., Vaughan Seed Co., Chicago, Peter Henderson & Co., New York, to 

 whom thanks are due: 



D. M. Ferry d Co. 



Perfection White Apple June Pink 



Buckeye State Early Detroit Golden Queen 



Ponderosa Early Michigan Dwarf Champion 



Peach Stone Chalk's Early Jewel 



Magnus Acme Coreless 



Beauty Matchless Earliana 



^^The leaflets not inoculated acted as checks. 



