As well known, the morphological characters of woods have important effects on the pulp and paper manufacturing, as well as their chemical and physical characters.
The qualities of pulp, paper and rayon fibers will be greatly affected by the morphological natures of the original raw woods from which they are produced.
It can not be overlooked that some difficulities with which we often meet in the course of pulp and paper manufacture, which are not easily solved without the knowledge of morphology.
In this review, recent reports and works dealing with such morphological problems were presented and discussed.
We classified these problems as the following subjects and discussed from our own standpoint.
I. The wall structure of fibrous cells.
II. The fine structure of cellulose.
Micells and Fibrills. The orientation of fibrills in the tracheid cell wall.
III. Lignin and Polyoses.
IV. The effect of digestion on the morphological structure of fibers.
V. The relation between the morphological structure of cell wall and the swelling behavior :
The paper strength as regard to the swelling behavior, Swelling and lignin, Paper strength, Mechanism of swelling.
VI. The relation between the morphological structure of fibers and pulp characters :
Fiber length and paper strength, The thickness of the fiber wall, Spring wood and summer wood, Paper strength with special reference to the primary wall, the Ultramicroscopic structure of the cell wall and the paper character, Sulfite pulp and sulfate pulp, rayon pulp (or dissolving pulp.)

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1) Noncrystalizable resin : its separation and quantitative determination.
A substance was separated in crystals three times in succession from the sodium-carbonate-soluble content of the ether extract of pitch and noncrystalizable resin was left unextracted. Quantitative determination by paper chromatography disclosed that the resin was unsaturated fatty acid and the crystal resin acid. The two substances were next analized quantitatively by TwitchelPs method based on the difference in the rate of esterification between fatty acid and resin acid, as follows :
2) Fatty acid content of pitch.
The methyl esterized form of the fatty acid separated from the sodium-carbonate-soluble component of pitch was fractionated on distillation at reduced pressure into 50% liquid ester of fatty acid and 50 % undistillated residue. The free fatty acid obtained from this ester on saponification with 1 N alcoholic KOH ga to the spot denoting Rf for a mixture of oleic acid and linolic acid on separation by paper chromatography. The result was reexamined by disolving the free fatty acid in a solution of caustic soda and oxydizing the mixed solution with potassium permanganate. The dihydroxystearic acid and tetrahydroxysteatic acid showed plainly that the unsaturated fatty acid was mainly composed of oleic acid and linolic acid.
As saturated fatty acid was suspected to be contained in the fatty acid of the sodium-carbonate-soluble component, separative test was made by Twitchell's method. By method of paper chromatography and fractional distillation under reduced pressure of separated saturated fatty acid, the result was confirmed that palmitic acid and stearic acid were contained in the saturated fatty acid from the sodium-cabonatesoluble componet.
Paper mill Process Saturated fatty acid Unsaturated fatty acid It was reported in our previous paper that the ether soluble content of pitch is separable into sodiumbicarbonate-solubles, sodium-cerbonate-solubles, caustic-soda-solubles and neutral substances. The table below shows how the sodium-carbonate-soluble and caustic-soda-soluble substances are separable into resin and fatty acid
Unsaturated fatty acid % = 100% (saturated fatty acid %)
As will be seen from the forgoing result, pitch collected during each process, except that pitch stuck to the machine stone roll for the reason of its abundant fibers, are composed of ether insoluble components (ca. 1020%), which contain organic substances (ca. 80%) mainly fiber and inorganic substancgs %) and ether soluble components (ca.8090%), which contain strong acidic substance (ca.12%), unsaturated fatty acid (ca. 1023%, linolic acid and oleic acid), saturated fatty acid palmitic acid and stearic acid), pitch abietic acid (ca. 5070%) and unsaponifiable substance (ca. 928%) resen in all probability. Resin acid, existing in 2 or 3 times as much a quantity as fatty acid, is so high in viscosity as to make the resin practically inseparable, as stated in the previous report on the separation of crystalline resin.

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The authors have studied the effect of plasticized synthetic resin latex coating on the air resistance (AR) of paper. The commercial vinyl latices (see Report I) were plasticized with the emulsion of plasticizer and used. The film-forming temp. (T_f, see Report I) can be lowered by the addition of plasticizer.
The commercial kraft papers were coated with the plasticized latices of various concentration and dried at 40°C and some of the dried papers were cured at 120°C for 5 min.
The degree of plasticization of latex particles showed very interesting effects to the AR. To increase the AR, there was the optimum degree of plasticization concerning to the drying or curing temp. and when the plasticity of the latex particles was too high or too low, the AR increased only a little after drying.

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Using the 5 species of hardwood in Japan, ---beech, birch, linden, oak, and willow---the wood analysis, the sulfate cooking, the bleaching, the examination of paper strength and the chemical analysis of pulp were investigated, and then the relation between the properties of wood and the paper strength were studied. The results obtained were as follows;
i) It was found from the wood analysis that the lengths of the fibers of willow and oak were short and that oak and beech had much parenchyma and that willow and linden contained much ash, extractives and proteins.
ii) The cooking was easily done with short time except willow. The pulp yeild and quality were good.The bleaching was also well done.
iii) According to the examination of paper strength, willow and oak are inferior to the other species.It is supposed that the less paper strength depends on the short fiber length and the much parenchyma.The other factors effecting the paper strength are the intertwining of fiber and physical structnre of fiber, and these factors should be worse in wi low and oak.
iv) It is supposed that birch, linden and beech are most suitable for the paper making pulp, and willow and oak are more suitable for the dissolving pulp rather than the paper making pulp.

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Applying, as the first stage, the neutral sulphite semi-chemical pulping process to beech tree and other several hard wood species common in this district (Shizuoka Prefecture), we got unbleached pulps containing various amounts of lignin by varying Na₂SO₃ percentage addition from 14 to 20 on the basis of dry chips and digesting time at 170°C from 2 to 3 hours.
By treating, then, these unbleached pulps successively with chlorine solution, sodium hydroxide solution, and chlorite solution activated by the addition of acetic acid under proper conditions in accordance with each pulp quality, we obtained, in all the cases, bleached pulps with about 85 brightness in the yield of about 60 per cent on the basis of dry chips.
But, in the first place, the very low pulp strength and poor quality of the bleached pulps prepared from unbleached pulps having high lignin content which might possibly cause unfavorable effects at refining process, should restrict the pulp digesting conditions to such that would give unbleached pulp having less lignin content than 14 per cent.
Nextly, we found out that the bleached pulps having pentosan contents of about 23 to 24 per cent give the best pulp strength measured in bursting factor or breaking length. This favorable results can be realized by making the pentosan in wood chips remain in the bleached pulp in the yield of about 60 per cent.Thus utilizing the holocellulose in the wood in so high rate that has not been achieved by any other chemical pulping process, the present report process might be named "holocellulose pulp method".

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