Notices of Memoirs — Vegetafiun of tlic Coal Period. 33 



of secretory tissue. Auatomical characteristics of a Lepidotlendroid 

 type of stem ; great development of secondary tissue in the outer 

 cortex, little or no true cork, lax inner cortex. Lacunar tissue in 

 the roots of Calamites ; hollow appendages of Stigmaria. Indications 

 of xerophytic characters may be the result of growth in salt marshes. 



(4) Evidence as to the Manner of Formation of Coal. 



(a) The structure of calcareous nodules found in coal-seams ; the 

 preservation of delicate tissues, the occurrence of fungal hyphse, and 

 the petrification of Stigmarian appendages as evidence in favour 

 of the subaqueous accumulation of the plant-debris found in the 

 calcareous nodules. 



(6) Ordinary coal microscopically examined. Spores, fragments 

 of tissues, bacteria, and the ground substance of coal. Coal found in 

 the cavities of cells in carbonized tissues. Suggested non-vegetable 

 origin of the matrix of coal. ' Boulders ' and coal-balls included in 

 coal-seams. 



(c) Boghead, Cannel coal, and Oil-shales. Recent investigations 

 of Bertrand, Eenault, and others. The structure and mode of origin 

 of torbanite, kerosene, shale, etc. Suggested origin of Boghead 

 from the minute bodies of algee [fleurs d'eau), spores, etc., embedded 

 in a brown ulmic substance found on the floor of a lake. Absence 

 of clastic material. Cannel coal characterized by abundance of 

 spores. 



{d) Paper-coal of Biissia. — The paper-coal of Culm age in the 

 Moscow basin consists largely of the cuticles of a Lepidodendroid 

 plant. Bacterial action as an agent in the destruction of plants and 

 as a factor in the production of coal. 



4. By J. E. Mark, F.E.S. 



(1) What is coal Y — A non-scientific term introduced into scientific 

 nomenclature for substances of divers character, and, therefore, 

 probably of different modes of origin. 



(2) Was the Carboniferous period one where conditions suitable to 

 formation of coal were unusually loidespread? 



Coincidence at this period of dominant giant cryptogams, extensive 

 plains of sedimentation, and suitable climatic conditions. Such 

 coincidence never occurred before or after the Carboniferous period. 



(o) What loorlc shoidd be done in order to advance our hwioledge 

 of origin of coal ? 



In the past light has been thrown on coal-formation by chemical, 

 petrological, palgeontological, and stratigraphical studies, and these 

 should be continued. 



(a) Chemical. — Importance of study of chemical composition of 

 fire-clays and other accompaniments of coal in addition to coal itself. 



(h) Petrological. — Dr. Sorby's work on origin of grains of 

 mechanically formed rocks (sandstones, etc.) should be continued. 



(c) Palaontological. — Studies of faunas and floras throwing light 

 on physical and also on climatic conditions. 



DECADE IV. — VOL. VIII. — NO. I. 3 



