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TWO NEW BRITISH SPECIES OF COMATEICHA. 



By G. Lister, F.L.S. 



(Plate o48.) 



The two minute species here described have been under observa- 

 tion for some j^ears. They both appear to be related to ComatricJia 

 laxa Post, and C. nigra (Pers.) Schroeter — species different enough 

 when typically developed, but connected by a series of intermediate 

 forms. A single development of C. nigra may produce along with 

 robust sporangia, each crowned with a mop of dense and intricate 

 capillitium a few curious dwarf sporangia, with much laxer and less 

 flexuose capillitium, somewhat resembling dwarf forms of C. laxa. 

 It was with such dwarfs that we attempted to class the two forms 

 now under consideration. Thanks however to the Pev. William Cran, 

 to whose unusually keen vision and careful observation students of 

 Mycetozoa owe so much and to whom most of our knowledge of these 

 new forms of Gomatricha is due, it is found that their characteristic 

 features remain unchanged in repeated developments; it therefore 

 seems desirable that they should receive specific distinction, and not 

 merely be regarded as varieties of well-known species. 



Gomatricha cornea G. Lister & Cran, sp. n. 



Plasmodium colourless. Sporangia scattered or solitary, stalked, 

 globose, dark brown, 0-12 to 0-32 mm. diam. Stalk subulate, sLnider, 

 erect, 0"17 to 0"2 mm. high, dark brown above, shading into brownish- 

 3^ellow below where it expands into a small discoid hypothallus, ringed 

 where it merges into the columella with a well-defined dark collar. 

 Columella C3dindrical, slender, reaching one-third to one-hilf the 

 height of the sporangium, forking or dividing above into the few 

 primary branches of the capillitium. Capillitium of rather rigid dark 

 brown threads, forking and branching repeatedly often at a wide 

 angle, without or rarely anastomosing, ending at the surface in short 

 diverging branchlets. Spores 8-5 to 2 fi diam., grey when highly 

 magnified, marked with minute scattered warts. 



Habitat. On bark aud moss, Westhill and Kirkville, Skene near 

 Aberdeen. Mr. Cran first observed this species in March 1913 in 

 company with Kj/menoholus farasiticus Zukal, on mossy bark kept 

 under care indoors ; since then it has appeared twice again on his 

 cultures ; he also found it in the open on plane bark at Kirkville 

 in the summer of last year. The sporangia occur singly on bark or 

 more often on the leaves of a moss {Orthotrichum sp.). The structure 

 of the stalk is unusual ; when mounted in glycerine it has the general 

 appearance of a thick-walled hollow tube ; closer examination reveals 

 within the smooth walls of the tube a central strand of parallel pale 

 brown fibres. In other species of Comatriclia the stalk is usually 

 black and opaque throughout; sometimes, however, as in the succeed- 

 ing species, C.finihriata, and in minute forms of other species, it is 

 paler towards the base and encloses a loose network of dark inter- 

 lacing strands. The yellow-brown base of the stalk is conspicuous in 

 fresh specimens of C. cornea ; after long preservation in glj^cerine the 

 whole of the stalk and the capillitium are apt to assume a yellowish- 



JOUKXAL OF BOTAXY. VoL. 55. [MaY, 1917-] K 



