87 



farmer gave it up because he found out the significance of a 

 hedge of buckthorn just across the road. On this hedge and on 

 buckthorn in the college woods one may find, each May, the 

 alternate stage of the oat rust. 



These grain rusts are of special interest because the records 

 of their occurrence carry us back to the beginnings of knowl- 

 edge about rust fungi. The Romans called rust Rubigo and 

 worshipped the god Rubigo each April as a protection against 

 rust. The name is perpetuated in the name of one of the wheat 

 rusts, Puccinia riihigovera. (11) By the help of the microscopes 

 of the eighteenth century rusts were recognized as plants and 

 called fungi. The Italian, Fontana, in 1767, made a very credit- 

 able drawing of spores of wheat rust and states that they "are 

 very minute plants that nourish themselves at the expense of 

 the grain." Fontana was an enthusiast over microscopic study 

 and recommends more looking and less theorizing: "The talents 

 of many learned botanists could be used to greater advantage 

 in the little-known fields of the vegetable kingdom, if, instead 

 of furiously pursuing new systems and enriching with new 

 barbarous words one of the most delightful and perhaps the 

 most useful branches of the science of nature, they observed 

 the structure of plants more closely . . . ". (31) Perhaps because 

 men did not follow this advice, gross misconceptions about the 

 nature of rust fungi persisted until de Bary, by his researches, 

 made a real science of the study of fungi. (11) 



At first no different species of the grain rust were distin- 

 guished but gradually it became clear that the grain rusts are 

 strict specialists, that wheat rust will not infect oats, nor 

 the reciprocal. As the facts stand today the story is even more 

 amazing. The same Jakob Eriksson whose "Mycoplasm 

 Theory" botanists did not accept is recognized as pioneer in 

 the work of distinguishing "form species" of the cereal rusts: 

 forms which look alike, which can be distinguished only "in 

 that every form is almost exclusively confined to its particular 

 cereal and that consequently it is able to infect no other cereal 

 but that one." (24) Before 1890, Eriksson states, only three 

 species of grain rust were recognized: one on oats, one on wheat 

 and rye, and one, Puccinia graminis which was thought to be 

 able to infect all the cereals and many species of wild grasses. 

 By 1898 Eriksson had differentiated ten distinct forms of rust 



