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Methods Employed in Uredineal Culture Work. 



By Frank D. Kern. 



The first researclies which proved a positive relationship between 

 the different fruit-forms of the Uredinales not only played an important 

 role in the classification of these fungi, but invested a further study 

 with much interest. A flowering plant which would produce even two 

 separate and distinct sorts of fruit would indeed be a curiosity, and yet 

 these parasites exhibit from one to four kinds of fruiting bodies, and many 

 of them, seemingly to vary their existence, possess the power of living 

 upon two entirely unlike hosts. Further attempts at classification, as 

 well as all economic efforts to control the pests have demonstrated a 

 necessity for a more intimate knowledge of the life-history of these 

 parasitic plants. The connection between the different stages in a life 

 cycle is best shown bj- means of cultures, and the scientific importance 

 of these inoculation experiments can not be overestimated. 



Among the immediate advantages to be gained is the connecting of 

 unattached aecia with their later stages, and to ascertain the range of 

 hosts. Some rusts are doubtless restricted to single species of hosts, 

 both for their aecial and telial forms, but since cultures have shown 

 that some heteroecious species may have their aecial hosts belonging even 

 to different families of plants. It is evident that exact relationships can 

 be established only by morphological characters and field observations, 

 afiirmed by artificial cultures. In the autoecious species it is sometimes 

 impossible to tell how many spore forms there may lie. Such a specimen 

 can not be placed in its proper species on account of the close resem- 

 blance of some isolated spore forms. Cultures offer a ready solution 

 to this problem. 



Although the various processes in the cultivation of the rusts are 

 comparatively simple, so little has ever been said regarding the apparatus 

 and methods employed that a more detailed account does not seem out 

 of place. 



The spring months are the period when most of the work must be 

 done, as this is the normal germinating period for the resting spores, and 



