260 



difficult circumstances. Some types are found clear up to the 

 snow line which is here close to 19,000 ft. and only perpetual 

 snow is able to stop plant growth. One thing that puzzled me 

 for a long time was the increase of the number of species toward 

 the top of the mountains and passes, instead of a decrease with 

 the increased altitude. This is of course due to the larger amount 

 of rain and snowfall on the summits. 



I have not completed my catalog of the species I found in 

 this alpine desert country, but I do not think that it will include 

 more than four hundred forms including the cosmopolitan weeds. 

 In a single valley in Kashmir one can find more types, and so I 

 cannot recommend western Tibet to the hunter for new species. 

 It is a place where the struggle is not between plant and plant, 

 but between the plant world and a hostile environment, and one 

 can examine plant adaptations to some very definite climatic 

 conditions. 



NEW SPECIES OF GRASS RUSTS 



By J. C. Arthur and F. D. Fromme 



In attempting properly to account for all collections in hand 



while working upon the manuscript for the next rust number of 



the North American Flora, the following forms are found to be 



sufficiently distinct to be entitled to specific recognition. They 



are mostly recent discoveries, but such forms as P. Leptochloae 



and P. unica have had an uncertain disposition for a number of 



years. 



Uromyces Jacksonii sp. nov. 



II. Uredinia amphigenous and caulicolous, scattered, buUate, 

 oblong or linear, 0.3-1 mm. long, tardily opening by slit in the 

 epidermis, yellow; paraphyses none; urediniospores globoid, 

 21-26 by 24-30^1; wall pale yellow, moderately thin, 1.5-2 /x, 

 finely echinulate, the pores 6-8, scattered. 



III. Telia similar to the uredinia, long covered by the epider- 

 mis, blackish-brown; teliospores angularly globoid or ellipsoid, 

 19-25 by 20-30 /i; wall fight chestnut-brown, uniformly 1.5 m 

 thick, smooth; pedicel colorless, about half length of spore, 

 delicate. 



