PHYSARUM.] 
PHYSARACE/E. 
51 
angles of the threads and with large lime-knots ; some may have erect 
stalks enclosing much refuse, standing with others more weakly formed, 
containing little refuse matter and cernuous from the weight of the 
sporangium. As in all the Calcannesi the amount of lime in the 
sporangium-wall is liable to great variation ; where the supply is 
abundant it gives firmness and persistence to the membrane ; where 
it is scanty the wall is fragile or evanescent, as in the form named 
Tilmadoche nutans. In contrast with the latter, a robust form occurs, 
having a short stout stalk, often projecting within the sporangium in 
a conical point, with lime-knots of large size, either distributed among 
the capillitium or confluent in the centre ; between these extreme 
forms all shades of difference may be found, making it difl&cult to 
define even distinct varieties. Examination of a large series leads to 
the conclusion that P. leucopliceum is not a distinct species, but must 
be included under P. nutans. The name P. leucopliceuri has been so 
long established as applied to a well-recognised form, that it would 
have been desirable in some respects to retain it as representing the 
type of this species ; but as the name P. nutans was given by Persoon 
twenty-three years earlier than that by Fries, the rules of precedence 
necessitate its adoption. 
The diverging forms may be approximately described as follows, 
being arranged according to the amount of lime in the sporangium- 
wall and capillitium. 
a. violascens Rest., Men., p. 114; sporangium-wall iridescent, 
fragile, free from lime ; capillitium without lime-knots, stalk 
cernuous. Spores nearly smooth, 8 to 9 /a diam. 
/?. genuinum : sporangium- wall with thin, innate clusters of 
lime-granules, fragile ; capillitium slender with few flat expansions 
at the angles and few small lime-knots ; stalk cernuous. Spores 
nearly smooth, 8 to 9 diam. Tilmadoche nutans Rost., Mon., 
p. 127. 
y. leucophseum : sporaiigium-wall with abundant lime, some- 
what persistent, capillitium with flat, often perforated expansions 
at the axils, especially towards the base of the sporangium, lime- 
knots many or few, fusiform or rounded, 5 to 20 diam. ; sessile 
forms frequent ; stnlk erect or cernuous. Spores 8 to 10 ^ diam. 
P. kucophceum Fr., Sym. Gast., p. 24. 
S. ^ robustum : sporangium- wall with dense deposits of lime, 
persistent. Capillitium stouter, with wide flat expansions, lime- 
knots rounded or angular, 20 to 50 broad, sometimes confined 
to the centre of the sporangium and confluent. Plasmodiocarp 
forms frequent. Stalk short, erect, stout. Spores more dis- 
tinctly warted, 9 to 11 diam. 
Plate XV.. A.— «. sporangia of form x 20 ; h. capillitium and spores, 
X 280 ; c. spore, x 600 ; d and d\ sporangia of form between § and 7, 
X 20 ; c. capillitium of d with abundant lime-knots, x 280 ; /. capillitium 
of d\ with few minute liinc-knots, x 280 (England). 
Vj.—a. sporangia of form 7, x 20 ; h. capillitium aud spores, x 280 ; c. 
sporangia of form 5, x 20 ; d. capillitium and spores, x 280 : <: snore, x GOO 
(Englaml). ^ ' 
The type of Til. (jrucUejita Rost., in the Strassbnrg collection, has 
small, nearly globose sporangia of the form (i, aud of a greyish- white 
