[Vol. 12 

 224 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



many species of Odontia where they are clustered together in the 

 granules, but in the present species such cystidia are distributed 

 along an even hymenium devoid of granules. 



Specimens examined: 

 Canada: J. Macoun, 20; St. Lawrence Valley, J. Macoun, 14- 

 Manitoba: 52 15' north latitude, Swan River, G. R. Bisby, 1047, 



type (in Mo. Bot. Gard. Herb., 59034). 



7. P. exigua Burt, n. sp. 



Type: in Mo. Bot. Gard. Herb, and N. Y. Bot. Gard. Herb. 



Fructifications effused, small, circular, gregarious, thin, some- 

 what membranaceous, tender, small pieces separable when 

 moistened, snow-white, even, contracting in drying and cracking 

 into polygonal masses 1-2 mm. in diameter, with the white 

 arachnoid subiculum visible on the sides of the fissures, the 

 margin narrow, white, arachnoid; in section 150-180 \i thick, 

 not colored, with some hyphae densely arranged parallel with 

 the substratum and then ascending and loosely interwoven to the 

 hymenial layer, about 3 \l in diameter, thin-walled, not nodose- 

 septate, perhaps slightly incrusted in the hymenial layer; no 

 gloeocystidia; cystidia incrusted, cylindric, 30-60 X 6-7 [i, con- 

 fined to the hymenial layer and usually wholly immersed, a few 

 protruding up to 12 (j. beyond the basidia; spores hyaline, even, 

 4-5 X 2}4 I*. 



Fructifications 1-12 mm. in diameter 8 in an area 4x1 

 cm. and probably becoming confluent. 



On bark of dead, fallen limbs, about 12 mm. in diameter, of a 

 frondose species. Mexico. December. 



P. exigua is distinguished among our species by its clustered, 

 small, snow-white fructifications which crack into small polygonal 

 masses. 



Specimens examined: 

 Mexico: near Guernavaca, altitude 4500 m., W. A, & E.L. Mur- 



rill, 877, type, and 378 (in Mo. Bot. Gard. Herb., 54474, 



54473, respectively). 



8. P. laxa Burt, n. sp. 



Type: in Mo. Bot. Gard. Herb. 



