54 Mycetozoa of North America 



Distribution: Common in the United States; Ontario, Puerto 

 Rico, Quebec. 



Illustration: Lister, Mycetozoa ed. 3. pi. 43. 



The typical form is found in great abundance on composts and 

 other piles of decaying vegetable matter, or manure. The small, 

 delicate, somewhat flattened and umbilicate sporangia, on reddish 

 stalks, have a superficial resemblance to Didymium xanthopus. 

 The lime in the wall and capillitium is usually scanty, although 

 occasionally denser. Intermediate forms, usually on wood, form 

 a series approaching and ending in the one figured by Lister in the 

 Monograph on pi. 43, fig. c, and formerly known as P. calidris. 

 This is larger, more robust, with dense lime in the sporangial wall, 

 and Badhamia-Vike lime in the capillitium. The shape of the 

 sporangia is globose or obovoid, and not umbilicate beneath. It 

 is practically the same as P. ohlatum except for color. 



The following, distributed in various exsiccatae, are forms of 

 the present species: C. Roumeguere no. 4642 as Tilmadoche nu- 

 tans; de Thiimen no. 1498 as Tilmadoche nutans; J. B. Ellis, 

 N. A. F. no. 614 as Physarum leucophaeum; H. W. Ravenel no. 478 

 as Physarum leucophaeum; H. W. Ravenel no. 479 as Physarum 

 nodulosum. This applies to the specimens in the Herbarium of 

 the New York Botanical Garden, but sometimes the material dis- 

 tributed in exsiccatae is not all alike. 



31. Physarum didermoides (Pers.) Rost. Mon. 97. 1874. 



Spumaria? didermoides Pers. Syn. Meth. Fung. xxix. 1801. 



Plasmodium white (Lister). Total height 0.5 to 1.3 mm. 

 Sporangia stalked, erect, and obovoid, ellipsoid, or cylindrical, 

 about 0.8 mm. high, 0.5 mm. broad, or sessile and obovoid or sub- 

 globose, crowded, white, or dark gray above from falling away or 

 discontinuance of the outer, calcareous crust; sporangial wall of 

 three layers, the outer a dense deciduous deposit of white lime- 

 granules, the middle layer a delicate, colorless membrane with 

 scattered lime-granules, closely combined with an inner purplish, 

 areolate, thicker layer. Stalk variable in length and thickness, 

 white, membranous, not containing refuse matter and rarely en- 

 closing lime-granules, rising from a plicate, white hypothallus. 

 Capillitium consisting of numerous white, rounded lime-knots, 

 connected by short, hyaline threads, which are purple at the at- 

 tachments to the sporangial wall. Spores very dark purplish 



