226 



The rusts so far considered are some of the more ordinary species, 

 belonging to the Aecidiaceae. There are species in both the Uredinaeese 

 and the Coleosporiacese, however, which seem to have the same ability to 

 maintain themselves indefinitely in the uredinial stage. 



Among the Uredinaeese two of the most common rusts are Melampsora 

 lledusw on Populus and M. Bigeloicii on Salix, both of which have secia on 

 Larix. The secia are so much alike that it is impossible with our present 

 knowledge to tell them apart. It seems well here, therefore, to consider 

 the two species together, although there are definite morphological charac- 

 ters in the urediniospores which mark them as clearly distinct from each 

 other. The collections of II. BigelowU in the Arthur herbarium show its 

 presence in nine counties of the State, the first collection being made in 

 1887 and the last one in 1914, both in Tippecanoe County. The rust is 

 common and the epidemic is usually severe- The only explanation which 

 seems reasonable for not having collections from all counties in the State 

 is in the lack of collectors being at work in those not represented. .1/. 

 Medusm is represented by collections from five counties in Indiana, and the 

 same remarks as to prevalence and severity that were applied to M. Bige- 

 loicii apply to this species also. Both of these rusts have a range also far 

 to the southward and westward of this region. Their secia, to the present 

 time, have not been collected nearer this region than New York and Wis- 

 consin. However, it is likely that they do occur nearer because the larch 

 has a range extending as far south as northern Illinois and northern 

 Pennsylvania. It also occurs occasionally as an ornamental tree at various 

 places in the State. The secia probably occur within the hundred eighty 

 mile distance from the northern half of the State and perhaps from all 

 parts of the State. It does not seem reasonable to think, however, that 

 secia occur within several hundred miles of the southern range of the fungi. 

 The natural assumption is, therefore, that they are able to pass the winter 

 in the uredinial stage. 



Bubahia Crotonis, on Croton monaiithogyiius, has been taken four 

 times in Indiana, from at least three counties, and over a period of time 

 extending from 1896 to 1912. It also extends as far north and west as 

 Nebraska. No secium is known for the rust, but the nature of the fungus 

 suggests a Pinaceous host and a cseomoid secium. Cceoma strohilinum on 

 Pinus palustris and Pinus tceda has been suggested by Arthur. 34 Neither of 



"Bull. Torrey Club 33:519. 1906. 



