[Vol. 2 



704 ANNALS OP THE MISSOURI BOTANICAL GARDEN 



spumeus, in which case the name should be written P. spumeus 

 Hornemann, Fl. Dan. pi. 1794. 1823, since there is no doubt 

 that Hornemann's figure represents P. spumeus as it is known 

 in Europe to-day. But the writer prefers to accept Horne- 

 mann 's plate as a correct interpretation of Sowerby 's species 

 (disregarding pi. 211) and write the name as P. spumeus 

 Sow. ex Hornemann. If the writer's theory is correct, there 

 never existed a plant, the name of which could be written as 

 P. spumeus Sow. ex. Fries, Syst. Myc. 1: 358. 1821, 1 since 

 Fries never illustrated the plant, and his descriptions, several 

 times repeated, were based, in part at least, on the erroneous 

 pi. 211 of Sowerby. 



In the American literature the plant was first described by 

 the writer in a recent paper. 2 The relation of Sowerby 's 

 figure to the species was not then understood and the state- 

 ment was there made that "the plants so referred do not 

 agree with the figure given by Sowerby, nor with Fries ' de- 

 scription." There are but few references to its occurrence 

 in this country, although it is a fairly common species. Lloyd 

 reports receiving it from several widely separated localities. 



Whether others may agree with the writer or not, the evi- 

 dence here presented should at least have the effect of doing 

 away with the inconsistency of citing both Sowerby 's illustra- 

 tion and that of Hornemann as representing the same species. 



P. spumeus is not likely to be confused with any species 

 except P. delectans. These two intergrade to some extent. 

 The former species has a strigose-tomentose surface to the 

 pileus while the latter is glabrous or only slightly tomentose. 

 Heavy rains or a little handling of the plant may cause the 

 pubescence on P. spumeus to become matted and appressed, 

 but when specimens are found growing imbricated so that the 

 lower pilei are protected by the ones above, the character is 

 very marked. The tubes in both species are long and slender, 

 but in P. delectcms the mouths are larger and more sinuous, 

 usually measuring 0.5-1 mm. in diameter, while those of P. 

 spumeus are smaller, measuring about 3-4 to a mm., and col- 



1 cf. Ann. Mo. Bot. Gard. 1 : p. 09. 1914. 



2 loc. cit. 



