134 THE NORTH AMERICAN SLIME-MOULDS 



fissure as in Physarum sinuosum Bull. In no American gathering 

 that I have examined does the capillitium show calcareous thicken- 

 ings as described by the British text. 



4. DiDERMA GLOBOSUM Persoon. 



Plate VII., Figs. 5, 5 a. 



1794. Diderma globosum Pers., Rom. N. Mag. Bot., I., p. 89. 

 1875. Chondrioderma globosum (Pers.) Rost., Mon., p, 180 



Sporangia more or less closely gregarious, sessile, globose or by 

 mutual pressure prismatic or polyhedral, white, the outer wall smooth, 

 polished, crustaceous, fragile, far remote from the inner, which is 

 thin, smooth, or rugulose, iridescent blue; hypothallus usually pro- 

 nounced and spreading beyond the sporangia, sometimes scanty 

 or lacking, columella variable, sometimes very small, inconspicuous, 

 sometimes large, globose, ellipsoidal, even pedicellate; capillitium 

 abundant, brown or purplish brown, branching and occasionally 

 anastomosing to form a loosely constructed superficial net; spores 

 globose, delicately spinulose, 8 /x. 



This species seems rare in this country. We have specimens from 

 Iowa. It is distinguished by small spores and generally snow-white 

 color. Lister has thrown doubt upon Rostafinski's definition of this 

 form — Mycetozoa, p. 78. Almost everything distributed in the 

 United States under this name belongs in the next species. Reported 

 also from Ohio, — Morgan. Washington. But: — it should be 

 found in Europe, where first described ! 



There are two ways to meet the difficulty. In the first place it 

 seems probable that a small-spored form really hides somewhere in 

 Europe. The difference between the Monograph measurement and 

 the size admitted for D. crustaceum Pk., evidently considered by Mr. 

 Lister as type and so used in his illustration, PI. 85, is too great to be 

 esteemed merely an error. That added .3 (Rost.) indicates caution, 

 the average of several measurements. Our D. globosum may repre- 

 sent what the Monograph describes.^ In the second place we may as 



^ Dr. Cooke, who used the microscope, applied the Monograph description 

 to British forms occurring on leaves; proceeded further and found the same 

 situation in New York. Mr. Massee gives the species wide range with spores 

 8-10 m; average 9 m; only a fraction too large; evidently none 12-15 M. 



