IMPORTANT SPECIES OF RUSTS 337 



crops of aeclospores throughout the hfe of the infected branch 

 or tree. 



Throughout the southeastern United States Cronartiinn qiier- 

 ciiim? and C. cerebnnn incite the production of stem galls on 

 pines. This stage (peridermium) on young trees causes dwarf- 

 ing and crippling. The uredinial and telial stages occur on the 

 lower leaf surface of various oaks. 



Cronart'mm coleosporioides (C. havknessii) causes the forma- 

 tion of stem galls on ponderosa pine and other pines of the west- 

 ern United States. The uredinial and telial stages of this rust 

 occur on certain Scrophulariaceae, especially species of Castilleja 

 and Pedicularis. 



Nearly a score of rusts having aecial stages on the needles of 

 various pines occur throughout North America. The aecial 

 stages of all are pink tubular protrusions, and all appear quite 

 alike. The uredinial and telial stages of each are restricted to 

 certain genera of comiposites, such as goldenrod or sunflowers, 

 or to species of Senecio, Parthenium, Coreopsis, Euthamia, Son- 

 chus, or Elephantopus. 



A group of widely spread rusts belonging to Uredinopsis and 

 Milesia attacks various species of firs. Ferns constitute their al- 

 ternate hosts. Uredinopsis viacrosperma on Fteridiinn aqiiUinhnn 

 can persist from year to year in the complete absence of firs. 



Several species of Melampsora attack larch foliage. One of 

 them, M. viediisae, bears pvcnia and aecia on species of Populus, 

 and another, M. bigelowii, on species of Salix. Melampsora lini 

 is widely prevalent wherever flax is grow n. It is full-cycled but 

 autoecious. Melampsora farlo-ivii, common on hemlock leaves, 

 twigs, and cones, has telia only. 



Throughout all tropical countries Cerotelium fici is the com- 

 mon fig rust. 



Hemileia vastatriXy \\ith peculiar urediniospores that are echinu- 

 late only on the exposed upper surface, has long been known to 

 cause a serious disease of coffee in the tropics of the Old \\'orld. 

 Although it has greatly restricted coflFee production there, as 

 yet it has not become established in the Western Hemisphere. 



The most important rusts on vegetable crops include Puccinia 

 asparagi on asparagus, Uromyces appendicidatiis on beans, Uro- 

 myces fabae on peas, and Puccinia siibnitens on beets. All are 



