148 Ciiiciiinaii Society of Natural History. 



I. M. spiNUivOSUM, Peck. Peridiuin globose, depressed 

 globose, sometimes elongated and often irregular, with a 

 thick, cord-like root. Cortex at first a thickish, white, 

 smooth, continuous layer; after maturity it cracks or becomes 

 furrowed into large polygonal areas, and at length falls away 

 in large flakes or scales; inner peridium very thick, at first 

 white and coriaceous, becoming hard, dry, brown and rigid, 

 the upper part finally breaking up into irregular lobes or frag- 

 ments. Mass of spores and capillitiuni compact, then friable, 

 at first olivaceous, then dark purplish-brown ; the threads 

 bent, curved and flexuous, subhyaline, .2-. 7 mm. in length, 

 about the same thickness as the spores, with a few short 

 branches, and with scattered prickles, which are most abun- 

 dant toward the acute extremities; spores globose, very 

 minutely warted, opaque, 9-12 niic. in diameter, often with a 

 minute or slender hyaline pedicel. See Plate \'., Figs. 13, 14. 



Growing on the sandy soil of the western prairies. Wis- 

 consin, Brown; Dakota, Ellis ; Nebraska, Webber ; Colorado, 

 Trcleasc ; Kansas, Kellerman, Cragin : New Mexico, Irish. 

 Peridium 2-4 inches in diameter. The plants are said to 

 grow together in groups, sometimes of many individuals ; 

 after maturity they are easily loosened from their place of 

 growth, and are then rolled about by the wind. It has been 

 stated that Prof. Peck's name is a synonym for M. corium, 

 Desv., but it is not clear what this species is. In Saccardo's 

 vSylloge the diameter of the spores is given as 8 mic, in 

 Grevillea X\'I., p. 33, Dr. Cooke gives their diameter as 15 

 mic; neither of these measurements apply to our plant. So 

 far as description goes, our plant appears to be the same as 

 the South American M. cliilcnse, Mont. Montague states 

 that he compared his plant with an authentic specimen of Af. 

 coriuni from Desvaux, antl tliat they differed in the color and 

 appearance of the capillitiuni and mode of branching of the 

 threads. With abundant specimens from widely different 

 regions of the west, I have been unable to detect l)ut this 

 single species. 



