194 REINHARDT THIESSEN 



The kinds of tissues represented in the coals. — In an examination 

 of a considerable number of sections from a number of coals, it 

 is learned that by far the larger proportion of the tissues remaining 

 represent woody parts of plants. By woody parts of plants is 

 meant parts of stems, branches, twigs, and roots, including all 

 the tissues, except the bark, that goes to make up such a part of 

 the tree or shrub. It cannot be said with certainty that the bark 

 has contributed to any extent to the constituents in question. 

 If bark is present at all in coal it finds its recognition possibly in 

 components appearing altogether different, which will be discussed 

 later. 



The anthraxylon of the dull coal then is derived for the most 

 part from rather small chips of semi-decayed woody tissues, such as 

 are prevalent in the peat bogs of today. Prosenchyma or wood 

 proper, and parenchyma such as cortex, pith, and rays are all met 

 with and are clearly distinguishable. There is, nevertheless, no 

 doubt that some of the structure seen in thin sections is derived 

 from the more succulent or younger parts of plants as well as from 

 herbaceous plants. Leaf-strands with some of the accompanying 

 tissues, petioles, and other vascular strands are frequently detected. 

 What appear to be deHcate tissues of plants are frequently seen. 

 The parenchyma of leaves is rarely observed, yet occasionally 

 structures are seen that could be construed as having been derived 

 from leaf parenchyma, and in some cases certain structures repre- 

 sent without a doubt leaf tissues in which all the leaf tissues, par- 

 ticularly the palisade cells, are well represented, and may be 

 favorably compared with the leaf tissues of a living Cycad. In 

 most cases the tissues contained between leaf cuticles have been 

 disorganized beyond identification. Occasionally tissues are found 

 in a fairly good state of preservation which as yet cannot be 

 correctly classified. In this connection spore walls or sporangia 

 should also be mentioned. Sporangial walls, either singly or in 

 connection with remainders of cones, are a common occurrence in 

 most coals, but particularly abundant in the coal from Buxton, 

 Iowa. Such spore walls are often remarkably well preserved. A 

 considerable amount of the woody tissues as well as other plant 

 tissues have been reduced to a finer state of division, exactly as is 



