824 THK itrsis of noxa scirriA. — fi{ \si:it. 



and, a.'^ far as kiniwii. aecia are never prodnced, yet it is very 

 roninmii. 



Tlie heteroec'ism of rusts was first suspected and established 

 in the wheat rust. 1\ gmminis. For years before botanists 

 made the diseovcry, practical farmers snspected that the bar- 

 berry, was connect(>d with the spread of wheat rii~t. in 1760 

 a law was passed in the State of Massachusetts for the destruc- 

 tion of l)arl>erry bushes. Tn 1816 Sclioeler, a ]3anish school- 

 master, ]danted small barberry bushes in the middle of a field 

 of rye and found that the rye around those bushes became 

 rusted while not a rust spot could be found in the rest of the 

 field. Tie also carried rusted barberry leavers into a field of 

 rye, and rubbed them on the rye ])lants till he could see the 

 "yellow dust" of the barberry leaves adheviiiii' to the plants. 

 These plauts were marked and were found to be the oidy ones 

 in the whole field which became infected ^\•ith nist. 15ut 

 botanists took no notice of these ex]ieriments oi' of fjirniers' 

 observations, as they believed the barberry fuucu-- au-l the rust 

 on rye belonged to different cenera. Tulasne showed that 

 the uredinia and telia. which up to this time had Ineu rea-nrded 

 as different genera, were connected. Tn 1S61 J)? P)ary 

 pointed out .that many of the rusfs had urediniospores and 

 teliospores and also that the latter aave vise to aeciospores. and 

 conversely the aeciospores to urediniospores. Tn 1864 he sowed 

 the teliospores of Piiccinia fjranv)iis on barberry and i)roduced 

 aecia. and in 1865 he sowed aeciosj^ores on rye and ]u-oduced 

 uredinia and telia, thus establishiiiir the connection of the 

 different forms. TTowever, it wa« not till about 1880 that the 

 heteroecism of the rusts was o-enerally accepfed. Since that 

 time many botanists have carried on infection experiments, so 

 that, the number of heteroeeious rusts now known amounts to 

 over 1 50 species. 



Much has been learned of the heteroecious rusts by infec- 

 tion experiments carried on by Euro|>ean and American 

 botanists. Tn America Farlow and Thaxter for eleven vears 



