194 



The Natuealist. 



plants, had they not been insulated? Several subsequent attempts 

 have been made for the purpose of settling the point, but as yet it is 

 an open question. 



Last year, Mr. Plowright, a well-known mycologist, carried out a 

 series of experiments on the following principle : — Thirteen lots of 

 wheat, obtained from different localities, were sown at different times, 

 and from each lot as many plants were infected with spores of JEcidiicm 

 berberidis, and an equal number of plants, called check plants, were 

 carefully protected from infection by being placed under bell-jars ; the 

 object being to contrast the per-centage of diseased plants in the two 

 cases. The following extract from " Grevillea," vol. lO, where the 

 experiments are described in detail, shows the result : — " Seventy- 

 eight wheat plants were infected with the spores of JEcidiimi berberidis, 

 and ninety-eight similar wheat plants kept as check plants against 

 them. Of the infected plants 76 per cent, developed Uredo in an 

 average of 24-4 days, while, in the same period, 70 per cent, of the 

 uninfected plants became spontaneously attacked by Uredo. One 

 experiment only (No. 2) out of the thirteen was wholly in favour of 

 the theory, and that lasted only 23 days. Still, 6 per cent, more of 

 the infected plants took the Uredo than of the uninfected. This is a 

 very small portion — ^far too small, in my humble opinion, to constitute 

 convincing evidence. I believe, however, that it can be accounted for 

 by my own negligence in not thoroughly cleaning the bell glasses 

 before using them to cover fresh plants. Had the last experiment 

 (No. 13) however, proved favourable to the theory, I should have 

 regarded it as being much more worthy of acceptance than I can now 

 do. It is only after much patient work that I felt myself bound to 

 differ from the eminent botanists abroad, who do accept the hetersecism 

 of Puccinia graminis as established beyond question." 



"Experiment 13. — The thirteenth, and final, experiment was con- 

 ducted on a totally different principle. The seed-wheat was poisoned 

 by steeping it in a solution of cupric sulphate ; and the ground in 

 which it was planted was watered with a solution of carbolic acid in 

 water. Two bell glasses, thoroughly disinfected with carbolic acid, and 

 the copper solution, were placed over both the patch to be used as check ^ 

 plants and over the i3ots containing plants to be infected. These bell 

 glasses were never touched until the plants were large enough to infect. 

 On the 20th August six were inoculated with JEcidium spores from 

 Narborough. A few days later — purposely choosing a day when there 

 was no wind — the check plants were reduced to six. The bell glasses 

 were not again removed until the twentieth day, when both patches 



