205 



ircroiis foes which. \n hen coiKlitioiis ai'c favoraljlc, very materially 

 rcihicc the yield and the value of the ('i-oi).'" ^^Mleat rust belong.-: to a 

 dixisioii of iMists known to botanists as /icfrro'cmnal, by which is 

 meant that the fungi causing these rusts de\elop in several appai'- 

 ently distinct stages or foi'nis. one of which appears on soma ])lants 

 very dissimihir to tho--e on whicii the Hrst form develops. In the first 

 or sunmier stage the wheat-inist fungi jirodiice what is called "red 

 rust." which may tievelop later in the season into the second stage, 

 know n as " l)hick rust." Black rust is nnich more injurious to the 

 crop than red rusi. Harly ripening varieties of wheat may, there- 

 fore, escape coinparatiAely unharmed, while those ripening late may 

 be l)adiy damaged by the rust. Fi'om the spores of the black rust is 

 developed a third form of the fungus, known as an (vcidinm, which, 

 however, does n(»t seem to be .necessary to the continuation of the spe- 

 cies, but constitutes a side form whose functions are not yet well 

 understood. The o:cklia do not grow on grain, but on very dift'erent 

 plants, " For Puccinia f/iriminis various species of the barberry have 

 been determined as capable of bearing the alternate form. The 

 buckthorns of the genera Rltdintins and Frmiyida support that of P. 

 co)'0)i(it<( ; and the aH-idium of P. ruhh/o-rera, the rust of which is 

 undoul)tedly the one most prevalent on wheat in Indiana, has been 

 found to grow upon various sj^ecies of the borage faiuily, such as the 

 common hound's-tongue (Ci/rtof/Io.'-fsi/ni ojp'cr,iale) , a roadside Aveed 

 in the older sections of the comitry." 



Observations made by the author seem to show that one species 

 {P. ruhif/o-rcra) of wheat rust, in its uredo (red) stage, is able to 

 pass the winter in the tissues of the natural Avheat plant, and to de- 

 ^'elop with great rapidity early in the spring. Among the conditions 

 ati'ecting the development of rust the following are mentioned : 



" In warm weather any conditions of the soil or atmosphere which 

 tend to keep the Avheat leaves constantly wet are conducive to the 

 rapid spread of the disease. Low-lying, rich soils are most subject 

 to the disease. Xo variety of Avheat is known to be nist-joroof, yet 

 some possess greater powers of resistance than others, Fulcaster, 

 Egyjitian, and Dietz Longberry are specified as among the resistant 

 varieties. Though not proved, an excess of nitrogen in the soil is to 

 be considered i)r()bably as liable to produce wheat easily affected by 

 rust. If fertilizers are to be applied to such lands, those containing 

 only inorganic elements are most advantageous so far as immunity 

 against rust is concerned. In districts liable to severe visitations of 

 the disease e-.trly i-ipeiiing wheats ai'e to b" pi\>feri-e(|. 



"Although the spores of the red I'ust are formed most abundantly 

 in the spring and early summer, they are also developed until late in 

 autumn upon various grasses, and may be wafted by winds to the 

 young wheat. Voltmteer growths of wheat upon old stubble fields 



