60 THE AMERICAN MONTHLY [March, 



That the infection is a result of either of these possibilities has not 

 been shown for the individual rust in question (^P. gram hi is) . 



Many rusts (Micropuccinete and Leptopuccinije) reproduce them- 

 selves by means of one spore, form only the teleutospore. And it may 

 be said that there seems to be no valid reason why the hetercecismal 

 rusts, though they produce several spore forms, might not do the same. 

 But the light of experiment is much against this theory. All attempts 

 to produce an artificial infection of the disease in the wheat plant through 

 the sporidia or the promycelium itself have failed. 



In my study of the rusts of this region, I am convinced that the greater 

 part of the " red" rust of wheat, usually attributed to Puccinia granii- 

 nisy is not the uredo-fruiting of that species but of a more common one, 

 P. r2tbigo-vera. This is a much earlier developing species than /*. 

 graiuinis — easily attaining maturity, the teleutosporic stage, before the 

 ripening of the wheat, while the teleutosporic form of P. graniinis 

 (the black rust of common talk) seldom appears before the harvesting 

 of the regular wheat crop of our Central and Western States. Yet it 

 usually does reach maturity in the oat fields and deserves more truly to 

 be deemed the common oat rust than to be called as it is " the common 

 wheat rust," though the application of such expressions is objectionable 

 and not to be commended. 



In this latitude I know Puccinia rubigo-vera to be able to live 

 through the winter in the tissues of the young plants of winter wheat. 

 At all times throughout the winter months of iSSS and 18S9, I had no 

 difficulty in collecting uredo rubigo-vera in quantity. I not only found 

 the mycelium in good condition, but was able by marking diseased 

 plants to observe the parasite begin the actual development of uredo 

 spores in early March. 



During the early part of winter pustules of urcdo-graiuiiiis were 

 also occasionally found, but not in sufficient quantity for extended ob- 

 servation. 



I think that the mycelium of neither of these two species can be con- 

 sidered truly perennial, as, for example, in Puccinia anemories^ yet in 

 favorable circumstances both wall be found capable of enduring the 

 winter — /. <?., they become essentially winter animals in the same sense 

 that wheat is a wmter animal, P. rubigo-vera being the hardier of the 

 two. And if in any part of this country conditions are favorable for the 

 wintering of the mycelium of P. graminis^ the winds, other atmo- 

 spheric conditions being suitable, may account for the sudden outbreaks 

 in any given locality. 



(3) If the fungus be proved perennial, what becomes of the teleuto 

 spores.^ The answer to this question can be placed upon tlie same basis 

 as for the following : If we prove that potatoes can be reproduced from 

 the potato ball (seed), what becomes of the tuber.? Tliat one spore 

 form can apparently perpetuate the species does in no manner prevent 

 another form from making an apparent surety more certain. 



Points of value yet in doubt : 



I. As in the case of P. rubigo-vera is the mycelium of P. graininis^ 

 a winter anitnal in some portions of our country } 



3, (a) Is the so-called P. rubigo-vera of this country identical with 

 the Eui'opean species of the same name } 



(b) If identical can the fecidium be developed upon other than the 

 borraginaceous plants already determined } 



Purdue Universitj, La/ay ette,Ind., November I2, i88g. 



