Arthur: Cultures of Uredineae in 191 i 59 



of the same species April 19, and characteristic telia were ob- 

 served May 3, without being preceded by pycnia or other spore- 

 forms. The species clearly produces but the one form of spore 

 in its life cycle. The aecia often found on this host are un- 

 doubtedly heteroecious. 



2. Aecidium monoicum Peck, on Arabis sp. Living plants of 

 some smooth leaved species of Arabis bearing aecia were sent by 

 Mr. E.- Bethel from Boulder, Colo., 5,000 feet altitude, and ar- 

 ranged May 9 over plants of Koeleria cristata, Stipa viridula, and 

 Trisetum subspicatum, followed by infection only on the last, 

 uredinia and telia being first observed June i. Similar plants 

 bearing aecia were also sent by Mr. Bethel from Lake Eldora, 

 Colo., 9,000 feet altitude, and placed over plants of Koeleria 

 cristata and Trisetum majus, followed by infection on the latter 

 only, uredinia and telia being first observed July 24. 



The results of the cultures appear unequivocal. The aecia 

 used belong to a form on Arabis, and probably also on related 

 genera, very common throughout the Rocky mountain region, 

 which infests the whole plant and usually prevents it from 

 flowering, consequently the determination of hosts is usually 

 difficult and often impossible. Whether all collections labelled 

 Aecidium monoicum Peck belong here may be left to future ex 

 amination, but most of them doubtless do so, although there may 

 be races going to different species of grasses. A bright yellow 

 form on Cheiranthus Menziesii from Nevada was named Aecid- 

 ium auriellum by Mr. Peck, and may be identical with the Arabis 

 forms, as the difference in color appears to be incidental. 



The telial phase has passed under the name Puccinia Triseti 

 Erikss., a name which belongs to a species with covered telia, 

 that has not with certainty been found in America. The rust 

 with similar naked telia on Koeleria and Stipa, Puccinia Stipae 

 Arth., is almost identical in morphological characters, but it forms 

 the curious Aecidium sclerothecioides E. & E. on composites. 

 There is, moreover, an adaptive distinction — the Trisetum form 

 is capable of germination as soon as the teliospores are mature, 

 while in P. Stipae the teliospores require a period of rest, and 

 first show their viable character the following spring. Telio- 

 spores from the first of the above recorded cultures were tested 



