GRASSES OF IOWA. 271 



ing to Cobb the species grows during the entire year. Some 

 years ago a systematic iavestigation was made of the rust 

 affecting cereals in the vicinity of Ames. While Paccinia 

 graminis was commo i in the fall, gradually disappearing on 

 the app'oach of cold weather, none of the sori were found dur- 

 ing the winter or early spring. It was not till the cluster cup 

 fungus appeared that this rust commenced to appear. Some 

 of the infest id plaits were removed to the green-house and 

 developed rust in abundance during the winter. 



COVERED RUST OF WHEAT. 



We may now discuss briefly two species of rusts, the Puc- 

 cinia glumarum and P. rubigo-vera, which are more or less com- 

 mon on wheat and some other grasses, and have very appro- 

 priately received the name of covered rust. 



Paccinia glumarum. — ^cidium unknown; the u'e5o sori 

 occur along the veins. The diseased leaf is frequen'ly of 

 irregular contour, color orange yellow, spores spherical, 

 or short, elliptical, spiny. Teleuto sori, grayish, covered 

 by the epidermis on the stalks and leaves, less frequently 

 on the flowers. Sori divided into chambers, surrounded by 

 paraphys's. Spares with short pedicels, mostly club-shaped, 

 unsym metrical; apex somewhat truncate, or with one or two 

 projections. This rust does not seem to h kve been generally 

 recogn zed as belonging to the description given by Schmidt 

 in 1819. It has been usually referred to as P. rubigo-vera. It 

 seems quite certain that most European mycologists who have 

 been. working wi'h the economic side of this question have had 

 the P. glumarum in mind. Eriksson and Henning say it is difli- 

 cult to say from the diagnoses of many writers who have dis- 

 cussed this question whether they had P. glumarum or P. dis- 

 persa. In European mycological works the secidium of this 

 fungus is said to be very common on common speed ^ell 

 {Litliospernum arvense) EcMum vulgare and Anchusa officinalis. 

 Common spaedwell is a very common weed in St. Louis and 

 other parts of Missouri and southern Illinois, but I have never 

 found the secidium on these weeds. 



It is very evident from the researches of Eriksson and Hen- 

 ning* that most wri'ers must have been working with a rust 

 very different than P. rubigo vera. On the question of the rela- 

 tion of temperature and the appearance of this rust, Eriksson 



•1. C. 146. 



