UREDINALES OF GUATEMALA BASED ON COLLEC- 
TIONS BY E. W. D. HOLWAY 
in. PucciNiA, Exclusive of Species on Carduaceae 
J. C. Arthur 
The two previous instalments of the present account of the rusts of 
Guatemala were published in this Journal (June and October, 1918, 
pp. 325-336, 420-446), and one more part is to follow concluding with 
an index. The present part lists 76 species, of which twelve are 
described as new, six are placed under new combinations due to dis- 
covery of additional spore forms, and a number heretofore known from 
South America are now added to the North American flora. 
Probably the most interesting group of rusts included in this part 
is that found on grasses. Grass rusts seem to be less common in the 
tropics than in the colder regions of the north, possibly because grasses 
are less abundant, at least where collectors go, or because these rusts 
are less conspicuous and so escape detection. The fine showing of 
fifteen species secured by Professor Holway, three being undescribed, 
is greatly to his credit as a close and discerning collector. Rather 
strangely, the two cosmopolitan rusts on corn and sorghum are not 
found in his material. 
Even more satisfying than securing hitherto unknown species is 
the discovery made by Professor Holway of the probable connection of 
an aecial form on Eupatorium to go with one of the grass rusts on 
Aegopogon. It will be a slow process to connect the alternate forms of 
heteroecious species in the tropics, as the chances for making succes- 
sive observations at the same locality and the opportunity to make 
cultures can come only at rare intervals. Professor Holway is to be 
congratulated on his fortunate find and clever observations in this 
direction. 
Less interesting, but equally difficult for the taxonomist, are the 
Salvia rusts. Although autoecious, they are given to forming only 
uredinia, and run into endless modifications. Pycnia and aecia are 
especially rare. Not until numerous collections on every species of 
462 
