[Vol. 2 



670 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



recourse to the microscope, for the microscope was unknown 

 when the foundations of this study were laid. In the separa- 

 tion of species other macroscopic characters of minor import- 

 ance were used. Color, pubescence, habitat, form, size, etc., 

 were characters that were largely drawn upon in fixing the 

 limits of species. 



It was unfortunate, however, that though the characters 

 named are the most conspicuous ones, yet they are more sub- 

 ject to modification and variation than are certain internal 

 characters that require the use of the microscope for their 

 detection. Perhaps the desideratum in systematic botany 

 would be a classification in which genera are well defined and 

 sharply separated from each other by gross morphological 

 characters, and in which the microscope would be necessary 

 only in determining specific characters. Perhaps this demand 

 is more nearly filled in the family Agaricaceae than in any 

 other group of the fungi. There the genera are divided into 

 sections on the color of the spores, and the genera in these 

 sections are more or less well differentiated on gross morpho- 

 logical characters. 



In those groups of the fungi that have been most carefully 

 studied, e. g., the Myxomycetes, considerable attention has 

 been paid to the minute anatomical structure of the plant. 

 Spore markings that are scarcely visible, except with an oil- 

 immersion lens, have been used as points of separation in 

 closely related forms, and in certain of the Discomycetes the 

 spore markings and the nature of the paraphyses have been 

 largely drawn upon to furnish specific characters. Durand 1 

 has gone somewhat farther, and in his studies in the fleshy 

 Pezizineae has taken into account the structure of the 



apothecium in fixing the limits of the families. Burt 2 has 

 recently set new limits to some of the genera of the Thele- 

 phoraceae, in keeping with their inner anatomical structure. 

 In the Polyporaceae, Miss Ames 3 has recently attempted to 

 outline a scheme of classification of the genera based largely 

 on the structure of the sporophores, but only a few forms 



1 Bui. Tor. Bot. Club 27: 463-495. 1000. 



2 Ann. Mo. Bot. Gard. 1: 105-190. 1914. 



8 



Ann. Myc. 11: 211-253. 1913. 



