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VOLUME XLIV 



NUMBER 2 



Botanical Gazette 



AUGUST I go-] 



THE ALTERNATION OF GENERATIONS AND THE 



MORPHOLOGY OF THE SPORE FORMS 



IN THE RUSTS 



A. H. Christman 



(with plate vii) 



DeBary (8) was the first to establish the doctrine of heteroecism 



and explain the relationships between the fructifications occurring 



in a complete life-cycle of a rust having all of the spore forms. He 



first proved by inoculation experiments that sporidia from teleuto- 



spores of Puccinia graminis Pers. when sown on the barberry produce 



there the spermagonia and aecidia, and further that these aecidio- 



spores taken from the barberry will again produce infections upon 

 wheat. 



In case of rusts which do not show a complete series of these spore 

 forms it has been supposed and is still assumed to some extent that 

 the missing stages exist, but are simply unknown in their correct 

 relation to the known spore forms. But the methods of cross-infec- 

 tion, first successfully used by DeBary (8, g)^ have led to the solu- 



many 



rusts 



that one or more of the spore stages found in rusts with a complete 

 life-cycle of the P. graminis type are regularly lacking in certain other 



4 



rusts. 



^psis 



^ _ — ^ „ ^ 



hemi-, lepto-, and micro- forms, with their abbre\nat( 



become of special importance since the discovery of sexuality and 



alternation of generations in the rusts. When comparing the com- 



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