56 BNDOSPOEE^. [PHYSARUM. 



membranous with innate clusters of white lime-granules. _ Oolu- 

 mella none, or represented' by confluent Hme-knots. Capillitium 

 of branching hyaline threads, with- numerous white lime-knots 

 varying in size and shape, sometimes confluent in the centre of 

 the sporangium or forming a Badhamia-like network with few 

 hyaline threads. Spores bright violet-brown, almost smooth or 

 spinulose, 7 to 10 /^ diam.— "Rost., Mon., p. 102, figs. 71, 72, 85 ; 

 Cooke, Myx. Brit., p. 13 ; Mass., Mon., p. 298 ; Maebride, in Bull. 

 Nat. ilist. Iowa, ii., p. 155, PI. ix., fig. 4. Ly coper don einerevm 

 Batsch, Elench. Fung., p. 155 (1783). Didymium scrobiculatum 

 Berk., in Hook. Jotirn. Bot. (1845), p. 66. Physarum scrobicu- 

 latum Mass., Mon., p. 300. 



Plate XVIII., A. — a. sporangia, x 20 ; J. capillitium and spores, x 280 ; 

 u. spore, X 600 (England). 



Plate XYIII., B. — a. sporangia, x 20 ; b. capillitium attached to colu- 

 mella and spores, x 280; c. spore, x 600 (Germany, Eostafinski's type of 

 Crateriacliea mutabilis). 



The capUlitium of P. cinereum varies widely in the development of 

 the lime-knots ; in the common forms they are very numerous and 

 rounded. Sometimes they are large and angled, and at other times 

 small with the hyaline threads profuse. They are usually equally dis- 

 tributed among the capillitium, but occasionally more concentrated in 

 the middle of the sporangium. A remarkable instance of the latter 

 state is seen in the form named by Rostafiriski Crateriachea mutabilis 

 (Mon., p. 126), the type of which is in the Strassburg collection. 

 Here the lime-knots are confluent, forming a distinct columella, a few 

 also appearing among the network of hyaline threads by which it is 

 surrounded. The sporangia are mostly elongated plasmodiooarps with 

 scanty, brownish-yellow hypothallus, but some are ovoid or subcylind- 

 rical, erect on a short brown stalk, the brown colofir extending into the 

 lower part of the sporangium- wall. The specimen issued by Raben- 

 horst and Winter from Pavia No. 2969 (B. M. 542), wrongly named 

 Didymium squamulosum, resembles Crateriachea in the sporangia being 

 occasionally provided with a short brown stalk, and in the lime-knots 

 being confluent and forming a pseudo-columella, but they are less 

 densely compacted and more distributed among the surrounding capilli- 

 tium ; the sporangia are also nearly globose. In the form named by 

 Cesati Didymium Neapolitanum (B. M. 573),* the lime-knots are con- 

 fluent, forming a large central mass more or less attached to the base 

 of the sporangium ; the surrounding capillitium either consists almost 

 exclusively of hyaline threads, or has a few large scattered lime-knots 

 in addition ; the sporangia are irregularly globose, sessile, or on a buf£ 

 foot-like hypothallus ; the spores in these three specimens are the same 

 as in P. cinereum. How far Crateriachea mutabilis, Didymium Neapoli- 

 tanum, and the Pavia specimen above mentioned may be held to be 

 varieties of P. cinereum, or as distinct species, must depend on further 

 gatherings establishing the constancy of their forms ; as the occasional 

 aggregation of lime-kaots is of frequent occurrence in other species of 

 Physarum, and in the somewhat nearly allied Badhamia panicea, this 

 character can scarcely be considered important. It appears from 



* Two species were issued by Kabenhorst and Winter under the name 

 Didymium Neapolitanum Ces., No. 2675 ; that in the Kew coll. (557) is 

 D. squamulosum, that in the British Museum (573) is the species above 

 described. 



