te. J. BUTLER 11 



boats. Had it extended through the air, it is remarkable that 

 it did not begin to spread until the collapse of the European 

 vines led to an introduction of living plants from its original 

 home. From Europe, its wider dist.-ibutiou on exported 

 vines and grapes is easy to unde: stand. 



The vine Oidium is another American species which spread through 

 Europe progressively after its first introduction. It was noticed 

 at Margate in 1815. and two years later was found in the 

 Rothschilds' greenhouses at Suresnes near Paris. In 1848, 

 it attacked other gardens near Suresnes and appeared in 

 Belgium. In 1849, it was all around Paris and next year was 

 in the Bordeaux district, in Spain and in Italy. In 1851, it 

 was all over France, Spain and Italy and was reported in 

 Switzerland, Hungary and all along the Mediterranean shores. 

 It is now known practically wherever the vine is cultivated. 

 A^ in the last case the species is native to America and did 

 not spread until introduced into Europe, probably on living 

 vines. If it could be blown across the Atlantic we would 

 expect it to have appeared in a number of places simul- 

 taneously and probably at a much earlier date. 



The oak mildew is a species allied to the last and, like it, is endemic 

 in North America. It was first seen in Europe about 8 or 10 

 years ago, but once introduced spread continuously (though 

 exceedingly rapidly) over the whole continent. The Oidium 

 on Euoni/mus japonicus, which is probably endemic in Japan, 

 is another similar case, which reached Europe about 1900 and 

 is now all over southern and western Europe. In both these 

 mildews the host plant was available to receive air-borne 

 spores long befoie the disease appeared, and both wore probably 

 nursery introductions. Several other instances of the same 

 kind will be found in the detailed list below (see Appendix I). 



Of diseases long known in Europe and more recently introduced into 

 the United States, the carnation rust is a good example. It 

 has been known in Europe since 1789, a time when fungi 

 attracted little notice, so that it may have been present long 

 before. It was not seen in the United States until 1890, when 

 it was found m Michigan. It did so much damage that it is 

 . not likely to have been overlooked previously. Another case 



