UREDINALES 85 



Doassansia has several species mostly in marsh or water plants 

 like Alisma and Sagittaria, the latter supporting two species. 

 Doassaiisiopsis affects similar plants ; among them Sagittaria has 

 two species, one forming gall-like bodies on the stems ; other 

 species are found in Potainogcton and Glyceria. 



The entire order forms a most interesting economic group. 

 With the exception of Doassansia and its allies, the American 

 species have never been monographed. The biological study of 

 certain species has been very extensive. 



LITERATURE. 



Saccardo. Sylloge Fungorum, 7: 449-527; 9: 282-291; ii: 

 174-230. 



Winter. Rabenhorst's Kryptogamen Flora Deutschlands, u. 

 s. w. ii; 80-131. 



Plow-right. A Monograph of the British Uredineae and Us- 

 tilagineae, 58-118, 272-301. 1889. 



Brefeld. Untersuchungen aus dem Gesammtgebiete der My- 

 kologie, ii and 12: 1895. 



Setchell. Preliminary Notes on the Species of Doassansia 

 Cornu. Proc. Am. Acad Sci. 26: 13-19. 1891. 



An Examination of the Species of the Genus Doas- 

 sansia Cornu. Ann. Bot. 6: 1-48. PL /, 2. 1892. 



Dietel. Die natiirlichen Pflanzenfamilien, i 1 **: 2-24. 1897. 



Order 2. UREDINALES. 



The order Uredinales contains the largest array of parasitic 

 fungi of any existing order and one in which there is an extensive 

 economic interest because of the fact that several very important 

 products are diminished by the ravages of these fungi ; wheat 

 and oats among the cereals, apples and quinces among the fruits, 

 roses and carnations among the ornamental plants, are only a few 

 examples of plants of economic importance that are parasitized 

 by members of this order. 



The rusts are further interesting because of the peculiar change 

 of host which takes place in certain of the species. To illustrate 

 this habit, the somewhat familiar examples of wheat-rust and 

 orchard-rust may be cited since the two parasites come to be of 

 economic importance in different stages of their life history, sim- 



