478 Dr. M. C. Stopes. On the Four Visible 



characteristic features. The three photos were all taken with identical 

 illumination, magnification, and time exposure. The fusain d6h^is (Plate 11, 

 fig. 6), is almost entirely composed of angular, fibrous, sharp-pointed frag- 

 ments of very varying size, black and opaque. 



The durain debris (Plate 11, fig. 7) is largely composed of irregular but 

 more polyhedrally shaped fragments, black and opaque, some of which have 

 transparent edges ; mixed with the opaque particles are clear, irregular 

 fragments, which appear to be portions of the broken up walls of the 

 macrospores. Scraps of cuticles, and so on, are sometimes seen, but are 

 seldom recognisable. The opaque fragments generally preponderate in at 

 least about the proportion of three to one. 



The clarain debris (Plate 11, fig. 8) is much finer as a rule, and consists 

 preponderatingly of clear, brown and amber coloured fragments of irregular 

 size and shape. Mixed with these are some opaque black granules and 

 fragments, possibly due to small inseparable streaks of durain. In tlie 

 clear clarain debris can be recognised many cuticle fragments, pieces of or 

 complete spores, and also oval or rounded particles which I have come to 

 the provisional conclusion represent the cell-contents in a special condition, 

 from which the surrounding cell walls have been dissolved away. 



Clarain debris repays study with the high magnification, but for com- 

 parison with the other two dSbris it is shown in the figure on the same scale. 



The Appearance of the Four higredients in Microscopic Sections of 



Untreated Goal. 



A number of carefully selected blocks and small pieces were cut without 

 any treatment save that necessary for sectioning by the grinding method. 

 The coal is consequently quite unaltered (save for the permeating Canada 

 balsam mixtures which attach the sections to the glass) both in appearance 

 and essential structure. The microscopic appearance of the four constituents 

 are most noticeably different and characteristic, as will be apparent on 

 reference to Plate 12, figs. 1-4 (coloured). 



Before describing them in detail, I wish to say a word about coal micro- 

 sections, many of which have been described by various authors. In several 

 publications there are available for reference a number of excellent photo- 

 graphic reproductions of the structure and appearance of various coal 

 sections. The reader should specially refer to Lomax (1911, 1915) ; White 

 and Thiessen (1913); Jeffrey (1914, 1915); and Hickling (1917); and for 

 critical references to the literature to Stopes and Wheeler (1918). All the 

 illustrations above quoted show the finely stratified lamellar nature of the 



