Williams news., 1921-04-29

eral matter. All are readily distin
 gufshable in the photomicrographs.
 Examination of a number of coaL
 has shown that most of the coal is de
 rived from the woody parts of plants
 such as trunks, stems, branches anC i roots, including all the tissues that
 make up such parts. Some of this
 wood is represented by the larger an
 thraXylon, some by the smaller an.
 thraxylon and some by the attritus | The proportion represented in each of | these varies in different coals and even
 at different levels in the same coal bed. There is evidence that some of the cellulose matter is derived from
 the more delicate tissues, such as her.
 baceous plants, young or growing parts
 of plants, leaf tissues, etc.
 The humic or decayed vegetable mat
 ter forms considerable proportion of
 the attritus of all coals. It is derived
 from the cellulosfc parts of plants, but
 includes, besides macerated, semi-de-
 cayed wood, some macerated gum,
 bark, pith, corteX and other more deli
 cate parts. There is no sharp dividing line between the anthraxylon and the humic constituents.
 Resins are found in all coals, but in greatly varying proportions, both in the anthraxylon and the attrituS. When found in the anthraXylon, the resin Is found in those tissues where 1t would be expected if the constituent were still sound piece of wood. In the attrituS the resins are easily diStin- guished from the other constituents.
 Comparing Different Goals.
 The exines or outer walls of spores are present in the attritus only and form an important part of all coalS, but In greatly varying proportions. The spore exineS are the most readily dis cernible constituents in all coals, and have definite characteristics. Different genera and perhaps different species of exines differ in sculpturing, size, form and thickness of wall, and by means of these characters can readily be distinguished from one another. The spore characters have been so well preserved in almost all coals that the spores of one kind of plants can be clearly distinguished from those of an- other kind. In some coal seams the | larger bulk of the spore exines are of | the same kind, in other seams two or | three kinds may form thee main bulk. | In comparing coals from different beds | he predOminating eXineS of one seam | ire easily seen to be different in some way from those of any other bed Thus he coals of different beds, containing liferent spores, may readily be dis fnguiShed from one another.
 Occasionally in a given coa; seam a pore exine is found that differs from hose of any other seam, but does not This Spore exfne may be
 distinguishing characteristic of the cal seam in question, although not the one. This fact promises 0 be of value in the stratigraphic cor elation of coal seams. The Pittsburgh cam, for example, contains a small pore exine that is both predominant nd characteristic and may thus be asily distinguished from any other.
 All ordinary bituminous coals con- ain certain constituents that are more ighly carbonized than the rest of the pal and stand out in sharp contrast | ) it on account of their OpaQueneSS. | general there are two types of car onaceouS matter-One type shows def lite plant structure and consists of Ae more highly carbonized parts of ant cells or bits of woody tissues or her plant tissues; the other shows ) plant structure and is of indefinite | .lgin. Other constituents that are fnvari- l lied rodletS or needles. Many are | | altered helter-skelter through the at itus. Sometimes they are present in | ch large numbers that they form a part of certain thin lami- Ie. Many of the anthraXylon compo- l. .nts, and, consplcuously, many of the
 neral charcoal constituents, inclose n smaller or larger number of rodlets [ at are evidently part of their struc- u re. Most of the tissues remaining in F e coal with which rodlets are assocf- t ed are recognized to be those of b ants related to the Medullosae, well- c own paleozoic plants allied to the V cads. From this it appears that me of the rodlets, If not all, are the q contents of the muciIage d. nals of Medullosa-like plants. In the n ginal plants these canals were elon- "A ted intercellular spaces containing d inning substances.