On Spores in the Carhonifcroiis Formation of Scotland. 87 



These are described as " Noncellular (or unicellular ?) plants 

 ibrmed of a thallus, distinctly limited, and of definite form. 

 Various forms, up to this time found on organic substances, 

 especially on the largest Triletes, are all parasitic, and attach 

 themselves to the organic substratum by their roots de- 

 veloped in a peculiar manner." ^ 



" The basal portion is developed into very small and short 

 branches, which, with thickened extremities, end in very 

 small knobs. 



"The apical portion is developed in the manner of an 

 elongated filament (TricJiostelium), or in a flat expansion 

 (SticJiostelium)." 



The two subdivisions are further defined : Stelide^, Sub- 

 tribus L, Trichostelium. 



"Thallus filiform, lower part joined to the substratum, and 

 changed into a pedicel of many branches ; the upper part vari- 

 ously developed. 1, entire ; 2, forked ; 3, much ramified, with 

 the ramifications arranged in verticils ; 4, much ramified, with 

 the ramification doubly bifurcated without order ; 5, ramifica- 

 tion irregularly dispersed." ^ 



Stelide^, Subtribus IL, Stichostelium. 



" Thallus undivided, entire, sessile, pedicel imperfectly 

 developed." ^ 



This group, his Stelidem (containing Trichostelium and 

 Stichostelium), we regard as an integral part of the spore on 

 which they occur, being in fact merely an extension of the 

 spore wall. This subject will be more fully entered into 

 when describing the macrospores provided with these so- 

 called Stelidece. 



There is another point from which some writers have 

 studied the occurrence of fossil spores, viz., the part they 

 take in the formation of coal. In 1857 the late Professor 

 Balfour called attention to the occurrence of numerous 

 spores (" seed-like bodies or sporangia ") in Fordel Coal ; * and 

 Professor Huxley, in his paper " On the Formation of Coal," ^ 

 ascribes to spores a place of the first importance. 



1 L.c, vol. i., p. 67. 2 j^c., p. 68. ^ jr ^^^ p, 72. 



•* On Certain Organisms found in Coal from Fordel — Trans. Eoy. Soc. 

 Edin., vol. xxi., p. 187. 



^ Contemporary Eeview, 1870, vol. xv., p. 618. 



