62 | Rhodora [Marcu 
made out in very thin sections, which allow a certain amount of light 
to be transmitted to the microscope. ће preparation of such sections 
of sufficient thinness is an almost impossible task in many instances, 
on account of the brittleness of the coal, which greatly enhances the 
difficulty of the grinding processes, employed in the study of the micro- 
scopic structure of minerals. ‘The writer in his studies on Mesozoic 
plants has acquired some experience in softening fossilized vegetable 
tissues, without essentially modifying their structure. An application 
of these methods to coal was without result, on account of the greater 
resistance of the material. It was found that neither aqua regia nor 
chlorate of potash yielded appreciable results in the desired direction. 
An aqua regia in which hydrochloric acid was replaced by hydrofluoric 
acid was finally tried with complete success. Even anthracite yields 
to its action in the course of a comparatively short time. Subsequently 
to exposure to nitrohydrofluoric acid for a sufficient interval, the coals, 
after careful washing, are soaked in hot alcohol containing from three 
to five per cent. of fixed alkali. ‘The latter process effects the swelling 
of the constituents of the coal without disastrous cracking and softens 
them so that they may be sectioned by the delicate methods in vogue 
in biological laboratories. As a preliminary to cutting, the fragments 
of coal are infiltrated with nitro-cellulose to bring them to a more 
favorable consistency. ‘The advantage of this method is, not only 
that it is possible to cut very much thinner sections than can be ob- 
tained by the grinding lathe of the mineralogist (3-5 micra), but that 
these sections may subsequently be bleached with nitric acid and 
strong chlorine water to almost any desired degree of decoloration. 
‘The present notice is mainly to indicate the botanical composition 
of certain true bituminous coals, known as Bogheads, as examined 
by the methods indicated above. It has been demonstrated, that the 
supposed Algae of Renault and Bertrand, are in reality the larger spores 
or macrospores of Vascular Cryptogams, which flourished during the 
Coal Periods. ‘The imagined Algae are in fact only the pores in the 
strongly sculptured coats of the spores in question. The apparent 
organization of the Algae as colonies forming a hollow sphere, is ex- 
plained as the highly sculptured wall of the macrospore surrounding 
its empty cavity. ‘The macrosporic nature of these remains is appar- 
ently placed beyond any doubt by the occurrence of the typical tri- 
radiate ridge on the face originally in contact with the three sister 
macrospores of the macrospore tetrad and by the very characteristic 
