160 REVISION OF THE NORTH AMERICAN HyDNACEAE 
of forms so that it is very difficult to characterize the species satis- 
factorily, and still more difficult to distinguish it from its congeners. 
It possesses scarcely one invariable character that is not common 
to other species, still the compact woody character of the sub- 
stance combined with its more or less orange tints will usually 
serve to distinguish the species. It has not been found possible 
to segregrate the many forms into any well-defined groups, and it 
seems necessary to regard the species as extremely variable in 
character. Moreover, single collections frequently show highly 
variable series of forms. This variable character has led to much 
confusion in nomenclature and in the broad view of the species 
taken in this paper most of the proposed species become reduced 
to synonymy. In fact the present treatment is practically a re- 
turn to the limits set by Schaeffer. 
Persoon first attempted to break up the Schaefferian group in 
his Commentarius, loc. cit, dividing the species as figured by 
Schaeffer into two parts. Plate 146, figures 1, 2, 3, 5 and 6 he 
referred to Hydnum compactum, and plate 146, figure 4 with plate 
147, figures 2-6 he referred to H. hybridum Bull. Later, in his 
Mycologia Europeae 2: 166, he somewhat doubtfully returned to 
the Schaefferian conception but retained the name H. compactum 
for the whole aggregation. In the meantime the segregation 
inaugurated by Persoon had been adopted by others, notably by 
Fries who referred the second group of figures from Schaeffer to 
H. aurantiacum (Batsch) Alb. & Schw. but retained the first 
group under Z7. compactum Pers. Тһе conception of the latter 
species appears to have undergone a gradual change until the 
M TA employed to designate a very distinct plant from the 
species of Schaeffer. It is, therefore, evident that. М compactum 
Pers. should be treated asa synonym of H. floriforme Schaef. and 
the species now designated Æ. compactum Pers. by the European 
botanists doubtless should be renamed. 
9. Hydnellum conigenum (Peck) 
Hydnum conigenum Peck, Bull. Torrey Club 30: 97. 1903. 
Plants mesopodous, on cones, small ; pileus obconic, subplane, 
dg somewhat round, 1-2 cm. wide; surface subpubescent, gray- 
I51-orange ; margins sometimes split, thin, obtuse; substance com- 
