May 13, 1910] 



SCIENCE 



753 



of a laboratory method for determining disease 

 resistance in the tubers. 



In cultures of the fungus on lima bean agar 

 and potato gelatin there were found, as reported 

 last year, certain immature spore-like bodies. 

 These have been found in similar cultures this 

 year and also what appears to be a more mature 

 stage, in the form of spiny, brown-walled resting 

 spores apparently produced ase.xually. These 

 have been found in all but three of the twelve 

 strains now in cultivation, these three being either 

 weak or recently isolated. 



The method of testing the disease resistance of 

 the tubers has been improved. Sterile living plugs 

 cut from the tuber to be tested for resistance to 

 Phytophtliora are inoculated with the fungus and 

 the amount of growth after nine to twelve days 

 is compared with that on plugs cut from tubers 

 known to be resistant or susceptible. In this 

 manner over eighty varieties of potatoes have 

 been tested and rated on a percentage basis as to 

 their tuber resistance. The ratings were found 

 to agree very closely with the relative tuber 

 resistance, as shown by the field experiments con- 

 ducted by Professor William Stuart. The prob- 

 able advantage of the laboratory over the field 

 method is obvious both in saving of time and in 

 precision of results. 



Some Studies on the Bean Anthraonose : Dr. C. 



W. Edgebton, Louisiana State Experiment 



Station. 



This includes the results of two years' study 

 on the bean anthracnose under Louisiana condi- 

 tions, including the period of incubation, meth- 

 ods of surviving the winter, relation of the fungus 

 to temperature and various soil microorganisms, 

 and the relation of the fungus to other anthrac- 

 noses. 



Under the best conditions for growth of the 

 fungus, the period of incubation is from four and 

 a half to six days. 



The fungus survives the winter by means of 

 mycelium in the seed and by spores. On the dis- 

 eased seed there are found some spores, at least 

 as late as February, that are viable, and spores 

 that are between the cotyledons in the seed, and 

 so protected, are nearly all viable at this time. 

 Spores are formed on the surface of the seed, 

 between the cotyledons in the seed, or in closed 

 pycnidial-like cavities in the tissue of the seed. 



The fungus is not able to live in the summer 

 months in Louisiana on account of the high tem- 

 perature. In cultures in the laboratory with 

 special care the fungus can be kept alive, though 



it makes a very feeble growth; but in the field 

 the disease is killed out entirely. When a mean 

 temperature of about 80° F. is reached with the 

 minimum above 70°, growth seems to be pro- 

 hibited. 



Various organisms in the soil, especially a spe- 

 cies of Fusarium, destroy much of the anthacnose 

 in the seed. This is accomplished by rotting the 

 seed, or by merely crowding out the anthracnose 

 in the spot itself. A large per cent, of the spots 

 on the cotyledons of young bean seedlings, that 

 grow from spotted seed in Louisiana, contain 

 Fusarium and no anthracnose. 



Inoculations with spores of the bean anthrac- 

 nose, have given abundant infection on bush beans, 

 slight infection on pole beans, slight infection on 

 Lima beans, and no infection on peas, young 

 cucumber plants, cucumber fruits, alfalfa and cot- 

 ton plants. Inoculations on growing bean plants 

 or young pods with anthracnose spores obtained 

 from fig, cotton, rose and pepper gave no infec- 

 tion, while check inoculations using spores ob- 

 tained from the bean gave abundant infection. 

 However, the treatment of healthy bean seed just 

 before planting with suspensions of spores ob- 

 tained from the cotton, fig and rose plants, re- 

 sulted in many eases either in the rotting of the 

 seed by the anthracnose or the spotting of the 

 young cotyledons. These spots, however, though 

 they contained anthracnose spores, did not look 

 like bean anthracnose spots, nor did they develop 

 further after the cotyledons were pushed above 

 the ground. 



Venturia inequali^, Ascospore Dissemination and 

 Infection: Mr. Ereet Wallace, Cornell Uni- 

 versity. 



The life history of Venturia inequalis (Cooke) 

 Wint. is in general well known to pathologists. 

 The conidial stage grows parasitically on the 

 leaves and fruit of the apple, causing the disease 

 commonly known as " scab " or the " fungus." 

 The perfect stage develops saprophytically on the 

 fallen leaves during the winter, maturing its 

 ascospores the following spring. 



During the spring of 1908 and a portion of the 

 winter of 1909, the writer gave some attention 

 to a study of a few details of some phenomena 

 connected with the perfect stage of this fungus. 

 In the spring of 1908 the method of ascospore 

 discharge was quite carefully studied. Two types 

 were observed, the one commonly known, by ex- 

 trusion of the asci through the ostiole of the 

 perithecium and another in which a circumcisal 

 dehiscence takes place, the upper half or more of 



