272 GRASSES OF IOWA. 



and Henning state from their extended observations that there 

 are marked differences in the disposition of the rust, depending 

 upon temperature conditions. It appears further from their 

 researches that the amount of precipitation was important in 

 the production of this rust. Concerning the ability of the 

 uredo spores to pass the winter in a living state in northern 

 climates, these writers found no evidence of it in the least, or 

 at any rate the conditions fo: this are extremely unfavorable. 

 It appears that in some cases where the snow covers the 

 ground during the spring, with a few slight frosts, the myce- 

 lium may be carried over, but its occurrence in this way is not 

 very common. On the other hand a long continued snow is 

 likewise detrimental. 



Pucclnia di.spersa. — This species of rust is apparently very 

 common in Europe. There are three different stages The 

 secidium stage produces circular or elongated, somewhat swol- 

 len, spots on the leaves, petioles and stem of several members 

 of the borage family. The spores are between 20 to 30" or 20 

 to 30 X 19 to 22". The uredo spores are spherical or short ellip- 

 tical; pale yellow, 19 to 29" in diameter. The tuleuto spores 

 long remaia covered by the epidermis. The sori chambered, 

 surrounded by numerous brown paraphyses; spores are mostly 

 club-shaped, unsymmetrical. Spores 40 to 50" long. Accord- 

 ing to Eriksson and Henning the uredo spores can germinate 

 in the fall. In addition to the above named hosts, this 

 rust has been found on several species of Bromus, Trisetum 

 and Triticum spelta. Its distributioi cannot be given because 

 in most ca-es the P. rubigo-vera included this as well as the 

 F. glumarum. It has been intimated above that the uredo 

 spores make their appearance on young germinating plants 

 in the fall, but it appears that the uredo spores are not 

 common the following spring. The inves igations of the 

 authors quoted here indicate that not in a single case was it 

 possible to produce uredo spores in the spring from those of 

 the autumn. 



L. H. Bolley, of Fargo, N. D., well remarks in regard to 

 several cluster cup fungi which occur on members of the 

 Borage family: "Several a3cidia of unknown life history 

 have been studied with reference to their relations to the red 

 rust of Pt^ccima rt^O/r/o-vera, many infectious t?sts being made 

 upon young wheat and oat plants, all with negative result?. " 



