The Cereal Rust Problem — Does Eriksson's Myco- 

 plasma exist in Nature? 



By Geo. Massee, F.L.S. 



The idea that the vegetative condition of parasitic fungi exists in the 

 tissues of certain host-plants, and is transmitted from one generation to 

 another, is not new. Berkeley (1), in discussing the subject, states as 

 follows : — " The mycelium of the cereal fungi is known to exist from the 

 earliest period in corn, and is perfected only under favourable con- 

 ditions." Worthington G-. Smith (2), in dealing with wheat rust, says : 

 " They all prove that Puccinia is hereditary ; that it exists in a finely 

 attenuated state in seeds from diseased plants, and can be transmitted 

 in a long interminable line from generation to generation." (3), " We, 

 as well as many other observers, have shown that seeds apparently 

 sound, will often, on germination, show disease in their seed-leaves ; 

 such plants are saturated with the germs of disease from their earliest 

 period of growth." (4), Writing on the supposed hereditary nature of 

 a disease affecting species of Dianthus, the same author states : " This 

 case has a distinct bearing on the allied fungus of corn mildew, Puccinia 

 graminis, which no one doubts is carried on from one generation to 

 another in the seeds. This being the case, and nearly every grain of 

 corn being probably saturated with the poisonous plasma of corn mil- 

 dew, the statements regarding the production of mildew on corn from 

 the contact of spores from a Barberry bush — the corn, it must be 

 remembered, being almost invariably infested with hereditary disease 

 — should be received with very great caution." 



The above statements are not supported by experiments, but ad- 

 vanced as the only apparently possible explanation of the repeated 

 occurrence of disease in those cases where external means of inoculation 

 were not evident. 



Quite recently Professor Jakob Eriksson (5), Director of the Ex- 

 periment Station of the Royal Swedish Academy of Agriculture, has 

 propounded a theory similar in substance to the ideas expressed by 

 Berkeley and Smith, and bearing on the subject of rusts attacking 

 cereals. The following quotations indicate the leading idea of the 

 theory : — 



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