23 



on the marked leaves while all the rest of the field remained free 

 from rust. 



This is the first real experiment in cultivation made in order to 

 prove the genetic relation of Aecidium berberidis to Puccinia graminis; 

 it was — seen with the eyes of the present time — far better planned 

 than Professor Hornemann's attempt to disprove the theories of 

 ScHBLER. HoRNEMANN (1816) cut holes in the leaves of grass to bring 

 the aecidiospores into them; Hornemann's experiment had a negative 

 result as was to be expected, but we must be surprised that his few 

 negative results were able to counterbalance the numerous positive 

 ones of Sch0ler; in fact the matter was temporarily settled by this. 

 In 1817 ScH0LER made several attempts to induce the Kgl. Landhus* 

 holdnings=Selskab (Royal Agricultural Society) to resume the matter, 

 but in vain. As late as in 1863 in his book on diseases of the plants 

 0RSTED (63 c ^^'') wrote that the barberry bush was innocent, an asser;: 

 tion he, however, had to repeal only three years later (0rsted 66). 



ScH0LER, however, not only dealt with Puccinia graminis he also 

 made experiments with the steeping of grain, wrote on Claviceps, 

 Ustilago etc. Even if he did not succeed in making his efforts appres 

 ciated by the Royal Agricultural Society or the leading botanists, he 

 had the satisfaction of seeing all the farmers at Hammel and in its 

 neighbourhood, destroy their barberry; he even enjoyed the triumph 

 that all the peasants of Hammel on the day after the death of his 

 most obstinate antagonist, bailiff Tommesen (1839) stormed his garden 

 and rooted up all the barberry bushes which Tommesen in sheer 

 defiance had planted there (Madsen 04). 



The theory that all parasitic fungi of the plants was a morbid rash, 

 caused by the quality of the soil, damp weather, deficient fecundation 

 etc., remained rooted a very long time in Denmark as also in other 

 countries. As late as in 1833 we find it maintained by Franz Unger 

 in his book "Die Exantheme der Pflanzen", in 1839 by A. F. Wieg* 

 MANN in "Die Krankheiten und krankhaften Misbildungen der Ge« 

 wachse", even Elias Fries was rather reserved on this question, and 

 would not consider Uredinales genuine fungi, and, in 1844, when the 

 Swedish potato^fields were spoiled by Phytophtora infestans, he des 

 fended this fungus with all his might, considering it only a secondary 

 phenomenon. 



But even if those theories did great harm because, as long as they 

 predominated, they prevented people from making all efforts to find 

 the right preventives against the diseases of the plants, practical agris 

 culturists continued to send in smaller accounts which, without attempt 

 ting to explain the causes, only stated the diseases of the cereals and 

 the preventives which had been tried against them. 



