166 IOWA ACADEMY OF SCIENCE Vol. XXYI, 1919 



"On Oct. 23, English rye showed 3 sori from timothy rust, tim- 

 othy showed 3 sori from timothy rust. 



"On Oct. 23, timothy showed 1 sorus from stem rust of oats, in- 

 oculated Oct. 18. 



"It is evident from these results that conditions were not present 

 in the greenhouse to induce rust upon any of the plants except tim- 

 othy, English rye and oats ; it is difficult to account for the sudden 

 appearance of timothy rust in the field, unless it was conveyed from 

 some other host plants, because the disease was not observed here in 

 1909 or previous to the middle of June, 1910. Red top was abund- 

 ant everywhere in proximity to the timothy and it was abundantly 

 rusted. It is probable, therefore, when the conditions are favorable, 

 that timothy rust will appear in epidemic form after having been in 

 some way transferred from related host plants. 



"Puccinia phlci-pratcnsis is evidently not the only rust on timothy. 

 The question of the secidium was discussed by us as follows : 



"Ericksson and Henning do not connect this fungus with an secid- 

 ium or cluster cup stage. These writers made a large number of 

 inoculation experiments upon barberry but without positive results 

 except a feeble infection in one case. Arthur, who reported on cul- 

 tures in Uredinfee in 1900 and 1901. says that Piiccinia poculiformis 

 from reed grass produces secidia upon common barberry. Ericksson 

 surmises that the secidium stage of this rust has dropped out as part 

 of the life cycle of the fungus." No secidium was observed on bar- 

 berry at Ames on the College campus in 1910 or 1911. 



This refers to barberry on the campus. Barberry has since been found 

 wild in several places, so that there probably was infection elsewhere in 

 the vicinity. 



THE RELATION TO OTHER HOST PLANTS 

 "The timothy rust has been reported by Dr. Ericksson and by Dr. 

 Lindau upon fescue and timothy grasses. There is the possibility 

 that this is only a form of the common grass rust. According to 

 Johnson timothy rust transfers readily to Arena sativa, Sccalc ccr- 

 eale, Festuca elafior. Dacfylis glontcrafa, ArrJicuatJicrum clatiiis and 

 Poa comprcssa ; negative results were obtained on wheat and barley. 

 Our own inoculation experiments indicated that it is transmitted to 

 a few other host plants of the grass family. It certainly did not 

 spread rapidly in the greenhouse. And while orchard grass was ob- 

 served diseased with Puccinia grani'niis in the field a little distance 

 from the timothy, red top was abundantly infected with P. grauiinis 

 at the time when timothy rust was spreading ra])idly among adjacent 

 plants of timothy. 



