HYMENOGASTRACEAE 41 



Zellcr and Dodge have referred to Rhizopogon several species in which the glebal 

 chambers are solidly tilled with black contents at maturity. Of these R. pachyphloeus 

 seems nearest our plant, and Dodge seems inclined to put it provisionally in thatspecies. 

 To us, however, it differs strikingly in the far greater development of superficial fibers, 

 its much thicker peridium, thinner tramal plates and very much smaller glebal cham- 

 bers. From R. diplophlocus, also with solid contents, our plant differs in the simple 

 peridium, larger glebal cells, smaller basidia and larger spores. We think the plant is 

 best treated as a Melanogaster, but with only one plant and no notes on the fresh con- 

 dition, we think the specific name somewhat doubtful. 



After referring to M. variegatus, Dr. Dodge in a letter says, "There is much closer 

 resemblance between your material and Melanogaster rubescens (Vitt.) as interpreted 

 by M. A. Curtis. He so determined (Ms. note in his copy of Schweinitz, specimen from 

 Schweinitz Herb, in Curtis Herb.) material collected by Schweinitz and referred by 

 Schweinitz to Rhizopogon acstivus Wulfen ex Fries.* The peridium of the Schweinitzian 

 specimen is about \ the thickness of your No. 5804 but it has a somewhat collapsed 

 appearance as do many of the older specimens which were repeatedly poisoned by the 

 old methods. The spores are much the same but darker than in your specimen. I have 

 never seen any authentic material of this species, so do not know whether Curtis's 

 interpretation is correct or not. Apparently Peters got the same thing in Alabama. 

 Your material has much lighter spores than anything I have ever seen in Melanogaster, 

 but I am not quite sure whether that is significant as in some other groups spores do not 

 assume their full color until late. For the present I am inclined to leave the specimen 

 in RJiizopogon pachyphloeus Z. & D. until I have had further opportunity to study 

 Melanogaster." 



The relationship to M. rubescens is indicated by the basidia, which are similar to 

 those shown in Tulasne's figure, and by the appearance of the peridium. 



Blowing Rock. Coker and party, No. 5804. Exposed on humus under chestnut and rhododendron, 

 August 26, 1922. 



Melanogaster ambiguus Tul. 



Plate 109 



Dr. L. H. Pennington has kindly sent us a section of a plant found by him in New 

 York and reported by Lloyd as M. ambiguus (Myc. Notes, p. 1065, fig. 2005). 



The dried section of the plant is slightly over a centimeter thick and has a con- 

 siderably wrinkled blackish bay peridium. In section the peridium is simple; about 

 300/i thick in dried condition and about 600ju thick when fresh (from prepared slide 

 of Pennington); composed of very irregularly interwoven threads with numerous 

 bladder-like swellings. Gleba jet black, the chambers rounded and filled with spores, 

 0.5-2 mm. wide; tramal plates very narrow, cream colored, contrasting strikingly with 

 the black spore mass. 



Spores 7.7-10.4 x 13-18^, most about 8.5 x 15.9/j, broad-elliptic, more or less 

 pointed at both ends, with a distinct cup-like prolongation at the proximal end, deep 

 brown in color under the microscope. Basidia 8.5-11.8 x 22-26/z, club-shaped, with 

 2-4 sessile spores; cavities filled with interwoven threads, 3-3. 7/j thick, which give rise 

 here and there to basidia. 



• Probably not in the sense of modern authors who use this name as an older name of Rhizopogon rubcuens Tul. 



