74 THK PLx-\NT WORLD 



that on the larger branches and to some extent on the smaller 

 ones, were knots and rows of excrescences with protuding 

 brown masses, now conspicuous by reason of the moist air 

 swelling the gelatinous matrix of the spores. Except in 

 color they reminded one of the well-known distortions pro- 

 duced by the black knot of the plum. A few feet away, and 

 forming a part of the same clump of shrubbery, were thorns, 

 probably Crataegus cerronis, on 'which Mr. Bethel pointed 

 out mummied fruit of the previous year, still showing remains 

 of a more than usually firm Roestelia. Other hosts, which 

 might harbor the aecia of this cedar rust, appeared to be 

 absent in the vicinity, and Mr. Bethel assured us that in a 

 number of visits to the place, when such aecia are at their 

 best, he had seen none other. Both these forms, aecial and 

 telial, have gone under names clearly inappropriate, and are 

 doubtless yet undescribed, * in spite of both being more than 

 usually conspicuous, due in large part to the conservative 

 method of using eastern or European names for western 

 plants so long as there is no authoritative denial. Portions 

 of branches bearing teliospores were taken, with which to 

 start cultures upon reaching home, and thus testing the 

 assumed connection between the forms of rust on thorn and 

 cedar. ** 



Some less striking examples of the same rust were 

 found before reaching Boulder, which was now not far off. 

 At fiv^e o'clock a call upon Prof. T. D. A. Cockerell in 

 Boulder, with some memorable discussion upon the probable 

 method of evolution of specific forms among the rusts, taken 

 over a cup of tea, and the active part of a very profitable day 

 in field observation and collecting came to an end. An 

 evening train took us back to Denver. 



The next day being Sunday we rested and tried to 

 make plans, but a heavy fall of snow in the latter part of 

 the day completely upset our calculations. Monday a beauti- 



* Since described and named by Mr. Kern, see Bull. Ton-ey Bot. Club, 

 n4:459. 1907. 



** The cultures were successful, see Jour. Myc. 14:23. 1908. 



