AND OTHER VARIETIES OF COAL. 121 



chemical changes. I know of no interpretation of these ap- 

 pearances, except that they are produced by free vegetable 

 cells, such as spores or pollen grains ; but yet I cannot con- 

 fidently affirm that they are such. Whatever they are, they 

 are always to be found in other cannel coals. 



5th. Scalariform tissue. Wherever a stigmaria is large 

 enough to admit of removal from the coal, scalariform tissue 

 may be found in it by thin sections, or the piaces where the 

 tissue exists may be selected by a common pocket lens from 

 any piece of coal containing fossils, as before pointed out. 

 In some places, the side view of these vessels shows their 

 ladder-like character nearly as well as a section of a fresh 

 fern, as in the section from which Plate IX., fig. 1, was taken ; 

 but generally only very small portions of the vessels are found 

 in a tolerably entire state, the rest being bent or broken into 

 fragments of such small size, that of themselves they could 

 not be recognised as belonging to such tissue at all. Such 

 are some of the fragments found in the dark matter bounding 

 the yellow bodies of the coal. The influence of the agent 

 which has broken up this tissue may be distinctly traced in 

 my preparations from parts which show distinct scalariform 

 tissue, to others which present a uniform brownish-red mass 

 devoid of all appearance of structure. The absence of scala- 

 riform tissue in a large number of sections by no means 

 proves that its occurrence in the coal is merely accidental, for 

 I have already pointed out that on all pieces of the coal con- 

 taining stigmariae, scalariform tissue can be seen in great 

 quantity by a common pocket lens. Why it does not appear 

 more commonly on sections, made promiscuously in the coal, 

 will easily be understood by all who have experienced the 

 difficulty of obtaining thin sections of pieces of coal contain- 

 ing a structure so different in density from its other parts as 

 scalariform tissue. This tissue exists plentifully in other 

 cannel coals. I have a piece of Capledrae coal, which has a 

 surface of three or four square inches covered with it. 



6th. I found in horizontal sections, reddish-coloured mem- 

 branes or expansions, as shown in Plate IX., fig. 6, giving off 

 from one of their surfaces a number of elongated and blunt- 

 pointed processes, not more than l-200th of an inch long, and 

 at their base about 1-lOOOth of an inch broad. And on ver- 

 tical sections I noticed bodies similar to that shown in fig. 5 

 of the same plate. These differ greatly in size, and vary in 

 colour from a bright yellow in thin sections to a bright or a 

 dark-red in thicker ones. They present almost uniformly the 

 appearance of reddish or yellow bands, bent so as to enclose 

 irregular elongated spaces, which are always narrow and 



