. Pulp and paper magazine of Canada. 2.—Vessels and Fibres of Poplar Wood PulpMagnified 100 Times. period of growth and formation. Thus the spring andsummer traeheids are broader and flatter, with thinnersidewalls than the autumn and winter traeheids, whilstin the case of the former the ends usually appearblunted. The ends of autumn and winter traeheids,however, are more inclined towards a spindle shape. December 15, 1916. PULP AND PAPER MAQAZINB Obviously then the period of growth to some extentinfluences the value of the fibre paper-making pur-poses. Coniferous tracheids usually exhibit the
. Pulp and paper magazine of Canada. 2.—Vessels and Fibres of Poplar Wood PulpMagnified 100 Times. period of growth and formation. Thus the spring andsummer traeheids are broader and flatter, with thinnersidewalls than the autumn and winter traeheids, whilstin the case of the former the ends usually appearblunted. The ends of autumn and winter traeheids,however, are more inclined towards a spindle shape. December 15, 1916. PULP AND PAPER MAQAZINB Obviously then the period of growth to some extentinfluences the value of the fibre paper-making pur-poses. Coniferous tracheids usually exhibit the character-istic pitted rings or circular pores; these are consti-tuted by actual holes in the fibres and sometimes, whena twisted fibre is viewed on the jolo, the presence ofthe pores gives rise to an apparently serrated edge. As we have before mentioned, the wood of differenttrees yields fibres or tracheids which vary from eachother in some pai-ticular. With a knowledge of thevariance, the student of paper-making materials may-. Fig. -Vessels and Birch Wool Fibres of CelluloseMagnified 100 Times. lie enabled to deteniiint witli some degree of certaintythe origin of the wood put]) fibres which he sets on toidentify. Dealing First With the Coniferous Series. Spruce wood is composed entirely of tracheids andyields a fairly characteristic fibre. The shape is flat,ribbon-like and the ultimate fibre embodies a numberof sharp twists or folds. Concentric double ring work-ings are generally to be observed, ranging from cir-cular to oval in contour, whilst occasional traces of thernedullaiy Iays are met within the form of parallelcross mai-kings between the pore marks. These me-dullary rays are the rays of cellular tissue seen in atransverse section of exogenous wood and which con-nect the ])ith with the bark. They are more prevalentin the wood of liioad leaved trees than the coniferseries. Tlie Iiiie tiacheids are very similar to spruce, butsliow single ling mai-kings in addition
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