754 MINNESOTA BOTANICAL STUDIES. 



" Coscinodon raui and Coscinodon renauldi," that his G renauldi 

 "is, perhaps, not sufficiently distinct from C. raui." The crit- 

 icism of'Cardot's species would doubtless have taken a different 

 turn had his attitude regarding the plant been generally known. 

 A most helpful feature, however, one for which all interested 

 students owe a debt of gratitude to the writer, is the clearing 

 up of errors made by the authors of the two species, Sullivant 

 and Austin. In .the light of these corrections the plants may 

 now be thoroughly well understood. 



From the dilemma regarding the right place of the little 

 Coscinodon I was not extricated even when Mrs. Britton kindly 

 loaned me type slides prepared from authentic material of C. 

 raui, which I examined and returned to her March 30, 1895. 

 She also kindly favored me with specimens of C. raui and C. 

 wrightii collected near Rapid City, S. Dak., by Mrs. T. A. Wil- 

 liams, and G. wrightii collected in Nebraska by Mr. H. J. Web- 

 ber. My method of examination was to remove some good 

 leaves from a well soaked plant, make a water mount, and in- 

 spect critically the surface of the leaves with a f in. and a \ in. ob- 

 jective. Prom the appearance of the leaves thus studied I could 

 not arrive at a satisfactory conclusion. There were uniformly 

 rectangular cells in the lower half of the leaves of all plants. 

 The cells in the upper half were usually roundish, more thick- 

 walled than below, but some leaves could be found on every 

 plant that had the cells in the upper part more or less elong- 

 ated, more so toward the costa, less toward the margin. Nor 

 was the bleaching of the leaf apex, the erose-dentate margin 

 in that part and the rounded leaf apex, a uniform character of 

 either species. Some leaves on either species were hardly dis- 

 colored at the apex, and then had the margin in that part en- 

 tire; others were discolored in the entire upper third, and then 

 were usually erose dentate in that part. To be sure, the leaves 

 of good Coscinodon wrightii were found to be, on the whole, 

 more rounded at the apex, the long subula rising rather ab- 

 ruptly above them; but some of the upper leaves, at least in 

 C. raui, are occasionally nearly as rounded, though the average 

 leaf apex was more acute than in C. wrightii. Not even the 

 diagnostic character laid down in Barnes' Key was found to 

 hold for C. raui, which there has assigned to it a hyaline hair 

 point shorter than the leaf. Mrs. Britton's correct figure 

 of a leaf taken from type material tends to modify this 

 diagnosis. And it is to be regretted that Barnes' new Key. 

 issued January, 1897, has, after two years of tacit refutation of 



