PHYSARUM.] 
PHYSARACE^. 
49 
Plate XIII., A.— a. sporangia closely combinetl, x 20 ; &. sporangia more 
or less simple, x 20 ; c. capillitium and spores, x 280 ; d. spore, x 600 
(United States). 
Under P. i^olymorphum is included Didymium ohrusseum Berk. & 
Curt, and Tilmadoche gyrocepliala Eost. 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. gT/rocejjhala, 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 P. 'polymorphuvi 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. glohuliferum) . In the 
type of Didymium ohrusseum 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. 
Hah. On dead wood, etc.— a. and /3. So. Carolina (B. M. 856, 862). 
a. Cuba (B. M. 440). /3. Pennsylvania (B. M. 860) ; Iowa (L:B.M.25); 
Ohio (L:B.M.25) ; Long Island, N.Y. (B. M. 1054). 
17. P. nucleatum Eex, in Proc. Ac. Nat. Sc. Phil. 1891, p. 
389. Plasmodium ? Total height 1 to 2 mm. 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 mm. long, 
longitudinally rugose, pale bulf, translucent above, without 
deposits of lime, enclosing refuse matter below. Columella none. 
CapilHtium a very close network of deKcate colourless threads, 
equal or with triangular expansions at the axils, with scattered 
minute rounded white lime-knots ; persistent after the dispersion 
of the spores. In the centre of the capillitium is suspended a 
calcareous shining white ball, O'l to 0-15 mm. diam., sometimes 
replaced by a compacted mass of irregular lime-knots. Spores 
violet-brown, minutely spinulose, 6 to 7 /x 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 80 ; c. capillitium and spores, x 280 ; 
d. spore, x 600 (United States). 
The type specimen of P. simile Rost., from Curtis, South Carolina 
(K. 1256), 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 cyliudi-ical 
columella would apply better to P. glohuliferum (Rost., Mon., App., p. 6). 
Hah. 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 lii-m, semi-traus- 
4 
