BIOLOGIC FORMS 



23 



EFFECT OF THE AECIDIAL STAGE ON BIOLOGIC FORMS 



GENERAL STATEMENT 



Eriksson (1894, pp. 292-309) was one of the first to suggest the 

 possibility of breaking down biologic forms by means of the aecidial 

 generation. He came to the conclusion, however, that this could not 

 be done, that, as far as the cereal rusts are concerned, they behave in 

 exactly the same manner when transferred through barberry as they 

 do in the urediuial stage. Salmon (1903, p. 159) and Marchal (1903, 

 p. 280) showed that with biologic forms of the Erysiphaceae the rela- 

 tions were exactly the same whether ascospores or conidia were used. 

 There is not an exact parallelism between the two since the cereal 

 rusts are heteroecious. However, the cases are somewhat similar since 

 a sexual fusion intervenes in both. Arthur (1910, pp. 227-228) con- 

 cludes that although there is distinct specialization of parasitism in 

 Puccinia poculiformis (Jacq.) Wettst. (Puccinia graminis Pers.) on 

 various grasses, this specialization breaks down in the aecidial stage. 

 The barberry would, then, serve as a bridging form between the vari- 

 ous grasses. Jaczewski (1910, pp. 356-357), on the other hand, does 

 not find this to be the case with biologic forms of Puccinia graminis 

 on cereals and grasses in Russia. His experiments support Eriksson's 

 claim that the barberry does not change the physiological specialization 

 of the various strains when they produce aecidia. 



EXPERIMENTS IN 1912 



In connection with the experiments described by the writer it 

 should be mentioned that the aecidia used in one set of experiments 

 were developed in the field but there was very slight chance for acci- 

 dental infection. Wheat straw very badly affected with rust in the 

 teleutospore stage was tied around barberry bushes. There was no 

 other rusted straw of any kind within considerable distance, so that 

 there was little chance of accidental infection. These aecidiospores 

 which were developed from wheat rust were transferred to wheat, 

 barley, oats, rye, and einkorn. The following were the results : 



RE&ULTS OF INOCULATIONS OF CEREALS WITH AECIDIOSPORES OF PUCCINIA GRAMINIS 

 TRITICI DEVELOPED IN THE FIELD 



Somewhat doubtful. 



