PHYSARUM.] PHYSARACE.E. 49 



Plate XIII., A. a. sporangia closely combined, x 20 ; b. sporangia more 

 or less simple, x 20 ; c. capillitium and spores, x 280 ; d. spore, x 600 

 (United States). 



Under P. polymorphv/m is included Didymium obrusseum Berk. & 

 Curt, and Tilmadoche gyrocephala Rost. I have not seen Rostafinski's 

 types of the latter. The specimens issued by Ellis and Everhart, 2699 

 N. A. F., and those received from Dr. Rex of Philadelphia and 

 Prof. Macbride of Iowa, under the name T. gyrocephala, agree with the 

 description given by Rostafinski. The colour of the sporangia varies 

 from grey to yellow in the same gatherings. Examination of the 

 capillitium and spores of these specimens and of the types of 

 P. obrusseum and /'. polymorphism shows that they are essentially 

 alike ; of the characters given above the clustering of the sporangia 

 cannot be held as of specific importance (cf. P. globulifrrnm'). In the 

 type of Didi/mium nbrt/xxcum Berk. & Curt., No. 532 F. Cub. 

 (B. M. 440), the sporangia are much compressed and undulated, and 

 are similar to the simple sporangia frequently met with in P. poly- 

 morphum. 



Hal. On dead wood, etc. a. and /3. So. Carolina (B. M. 856, 862). 

 a. Cuba (B. M. 440). /. Pennsylvania (B. M. 860) ; Iowa (L:B.M.25); 

 Ohio (L:B.M.25) ; Long Island, N.Y. (B. M. 1054). 



17. P. nucleatum Rex, in Proc. Ac. Nat. Sc. Phil. 1891, p. 

 389. Plasmodium? Total height 1 to 2 inm. Sporangia globose, 

 stipitate, erect or inclined, 0*5 mm. diam., white ; sporangium- 

 wall membranous, with scattered innate clusters of white lime- 

 granules. Stalk subulate or nearly equal, 0*7 to 1'5 rnm. long, 

 longitudinally rugose, pale buff, translucent above, without 

 deposits of lime, enclosing refuse matter below. Columella none. 

 Capillitium a very close network of delicate colourless threads, 

 equal or with triangular expansions at the axils, with scattered 

 minute rounded white lirne-knots ; persistent after the dispersion 

 of the spores. In the centre of the capillitium is suspended a 

 calcareous shining white ball, 0*1 to O15 mm. diam., sometimes 

 replaced by a compacted mass of irregular lime-knots. Spores 

 violet-brown, minutely spinulose, 6 to 7 /u, diam. 



Plate XIII., B. a. sporangia with the spores dispersed and only the basal 

 part of the sporangium-wall remaining, x 20 ; b. stalk and capillitium 

 showing the central ball of lime, x SO ; c. capillitium and spores, x 280 ; 

 d. spore, x 600 (United States). 



The type specimen of P. simile Rost., from Curtis, South Carolina 

 (K. 1255), has buff stalks without lime deposits, and delicate persistent 

 capillitium with a central mass of lime ; it is a poor development and 

 in imperfect preservation, but there can be little doubt that it is the 

 same species as P. nucleatum, although Rostafinski's description of 

 P. simile with the stalk continued into the sporangium as a cylindrical 

 columella would apply better to P. globuliferum (Rost., Mon., App., p. 6). 



Hab. On dead wood. Pennsylvania (L:B.M.26); Iowa(B. M. 1019). 



18. P. penetrale Rex, in Proc. Ac. Nat. Sc. Phil. (1891), p. 389 

 Plasmodium ? Sporangia erect, ellipsoid, rarely globose, 0'3 X 

 0'5 mm. by 0-5 x 0*7 mm., stipitate, grey or pale greenish- 

 yellow ; sporangium-wall membranous, rather firm, semi-traiis- 



4 



