[Vol. 2 



682 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



hyphal measurements given are for the hyphae in the con- 

 text of the plant and not for those in the subhymenial tissue. 



Statement of Problem 



The writer presents in this paper the results obtained by 

 carefully investigating some of the more common species of 

 pore fungi, using the methods outlined on the preceding pages. 

 There are certain groups of species in the Polyporaceae that 

 are very much in need of just such treatment, and it is to 

 these groups that the writer has turned his attention. The 

 groups consist of closely related species that have been 

 separated heretofore largely on external characters and in a 

 great many cases the results have only led to confusion. The 

 problem, as the writer saw it, was one involving a contribu- 

 tion toward a more exact characterization of these species and 

 their separation, wherever possible or feasible, on some con- 

 stant internal microscopic character. Some species are well 

 enough marked by external characters so that such distinc- 

 tions should be used only as supplementary characters, while 

 in other cases the characters obtained by this study should 

 displace those hitherto used. 



The results obtained were not as gratifying as was expected 

 when the work was undertaken. Only a small beginning has 

 been made, for it is a laborious task involving the cutting and 

 examination of many sections for each species in order to be 

 sure that the characters shown by the first sections are con- 

 stant for all collections of the same species. The work should 

 be carried on although several years would be required for 

 its completion. Permanent mounts of the sections have been 

 made for each species and these are available for future 

 reference. Criticisms and suggestions, both of methods em- 

 ployed and results obtained, are invited and will be given 

 careful consideration. 



ACKNOWLEDGMENTS 



Acknowledgments and thanks are due to Dr. E. A. Burt 

 of the Missouri Botanical Garden for aid, criticism, and ad- 

 vice in the preparation of the paper and for free access to 



