478 TF. C. Sturgis — Type- Specimens of Myxomycetes. 



authentic specimen of Link's species, the acceptance, as final, of 

 Rostafinski's judgment concerning it, seems unavoidable. 



DiDYMiuM ExiMiuM, Pk., Rep. XXXI, p. 41, 1878. A small bit of 

 the type of this species, consisting of a portion of a leaf bearing 

 three sporangia, was sent me by Professor Peck. It presents the fol- 

 lowing characters. 



Sporangia globose, slightly umbilicate beneath, 0.4-0.6™™ in diam- 

 eter, white, stipitate. Stalk slender, 1™™ long, golden-brown, longi- 

 tudinally wrinkled, expanded below and almost black from included 

 refuse matter, rising from a small hypothallus. Sporangium-wall 

 hyaline, colorless, beset with stellate crystals. Columella irregularly 

 subglobose, golden-brown. Capillitium scanty, consisting of deli- 

 cate, colorless threads expanded at their point of origin from the 

 columella. Spores rather dark, violet-brown, minutely spinulose, 

 7.5-9yLi in diameter. 



I have compared this specimen most carefully with a large num- 

 ber of autlientic specimens of Didymium nigripes (Lk.) Fr. and D. 

 xanthopus (Ditm.) Fr. in my collection, and with specimens dis- 

 tributed in Ellis & Everhart's N. A. Fungi, including two named by 

 Rex. D. eximium^ Pk. No. 412, in that collection, is the typical D. 

 microcarpon of Fries and Rostafinski, common everywhere, and 

 usually occurring on Sphagnum. No. 2089 is the same, differing 

 only in its habit (a dead herbaceous stem) and its slightly larger, 

 darker, and more distinctly spinulose spores.* Both show the 

 while sporangia, pale yellowish subglobose columellas and slender 

 brownish-orange stalks characteristic of Dldynihmi xanthop^is, Fr. 

 No. 1393, according to Macbride (1. c, p. 91), represents Rex's concep- 

 tion of Didymium nigripes (Lk.) Fr. The former notes the small size 

 of the sporangia, " about 4"™," and the correspondingly small spores 

 " 6-8/x." " Otherwise," he writes, " the species is hardly more than 

 a variety of the next " (Z>, xantJiopus^ Fr.). In this I can fully agree 

 with Professor Macbride. But Rex's specimen is hardly typical of 

 D. nigripes. An authentic specimen of the latter, furnished me by 

 Ml-. Lister, has pure white sporangia measuring 0.5™'" in diameter 



* It should be noticed that this specimen was distributed by Dr. Eex under 

 the name D. exhnium, Pk., that he recognized important differences between it 

 and the specimen later distributed under the same name (No. 2493), and that his 

 conclusion regarding these two specimens was expressed in the following words : 

 "They apparently form the extreme limits of what must be considered an 

 extremely variable species, the intermediate and connecting links of which 

 exist." (Proc. Acad. Nat. Sci., Phil., 1890, p. 195.) 



