TIIALLiiI'IIYTES; FUXGI 



283 



appc'iir : (1) ."porii/ia, wliicli develop the stage on tlie liarber- 

 ry ; (-2) (tcididsjiD/Ts, which deveh>p the stage on the \vheat ; 

 (3) liredospures, which rejieat the iiiyceliuni on tlie wlieat ; (4) 

 teIcutu><2Mrt:s,'^\\ic\\ hist througli the "winter, and in the spring 

 produce the stage bearing sporidia. It shoukl be said that 

 tliere are otlier spores of this plant produced on the barberry 

 (Fig. 53), but they are too uncertain to bo included here. 



The barberry is not absolutely necessary to this life cycle. 

 In many cases there is no available barberry to act as host, 

 and the sporidia germinate directly ujion the young wheat, 

 forming the rust-producing mycelium, and the cluster-cup 

 stage is omitted. 







\S. L> 



Fh;. --'14, Two species of " cedar apple '' ( Oy?)inosp&f'angiutn). both on the common 

 jiini]ier [JnHij'tr"^ VhghiU'i'fn.^A after Faklow, B after Encler and Pkantl, 



ls8. Other rusts. — 3Iany rusts have life histories similar 

 to that of the wheat rust, in others one or more of the 

 stages are omitted. In verv few have the stages been con- 



