Summary It is hard to obtain seeds from Pinus koraiensis crossed with P. tabulaeformis. According to the cytological investigations on both pines, the developments of each macrospore and microspore, the fertilization, the number of chromosomes and the causes of failure to get seeds, indicate that the incompatibility exists in these two species of pines. 1.The interval between pollination and fertilization of P. koraiensis is almost exactly 12 months, but that of P. tabulaeformis is 13 months. After the pollination has taken place, both the pollens stay at the pollen chamber of the tip of nucellus and will germinate until the average temperature is above 22 pollinations take place while the female gametophyte is still in a free nuclear stage. The mitosis of the central cell and the body cell of the pollen tube are at the some time, which in P. koraiensis is 102 days before fertilization, and which in P. tabulaeformis is 7days. 2.There is a big difference between the number of chromosomes of P. koraiensis and that of P. tabulaeformis. Chromosomes in the microspore mother cell of P. koraiensis is n=6, those of P. tabulaeformis is n=12; chromosomes in the endosperm cell of P. koraiensis is n=6, 70, those of P. tabulaeformis is n=12, n=14. As for the number of chromosomes the crossing of P. koraiensis with P. tabulaeformis is rather difficult. 3.The main cause of the incompatibility between P. koraiensis and P. tabulaeformis is the pollen of P. tabulaeformis showing poor or no germination in the nucellus of P. koraiensis. The ovule of P. tabulaeformis stopped its development at the free nuclear stage and is similar to the development of the ovule of P. koraiensis which is not fertilized.

The 33 kinds of bamboos (listed in Table 1) used in this experiment are those generally grown in the south-eastern and south-western parts of this country. For searching new fibre source, the fibre dimension, fibre volume and basic density were studied and arranged in groups according to their size. Such features as fibre length, cell wall thickness and the basic density may play the part in the assessment of bamboo-species suitable for pulping. The results are summarized as follow: 1.The average fibre lengths of the 33 species ranged from 1.70 to 3.19 mm (average 2.52 mm) and the average width ranged from 9.65 to 16.87μ (average 13.2μ) Though the average fibre length is situated between the coniferous (average 3—4mm) and broadleaved woods (average 1.4 mm), it appears mostly to approximate the coniferous woods. To compare with the fibre width of the coniferous woods (average 35μ), the average fibre width of bamboos is always low, even lower than the broadleaved woods (average 24μ). Therefore the bamboo-fibres are apparently slender than that of both coniferous and broadleaved woods. It can be revealed by the L/D ratio (the length to the width). Of these the bamboo-fibres usually stand between 115—290, mostly over 150; while that of the coniferous woods could not yet reach 100, especially that of the broadleaved woods (Table 2). To raise the density of paper the mixture ratio of long and short fibres is more important for the manufacture of chemical paper pulp. Data of the frequency and distribution of fibre-lengths has not yet been available on the pulp industry. From this statistical data of 33 bamboo-fibres the curves of the maximal frequency and distribution of fibre-lengths are shown in Table 3 and Fig. I, 1—33. 2.The 2W/1 ratio should be of particular interest to the paper making industry not only because of its desired strength of paper but also because of its different application. This ratio among 33 bamboos was found to be greater than unity ranging from 1.22 to 6.18 (Table 2). This might be a guide in practice for selecting the bamboosort and determinating the available blending with other than bamboo-fibres. 3.The proportion of fibres, vessels and parenchymas of 33 species was given in Table 4. For an economic returns, the volume of the bamboo should be at least over 30% and probably 50% of fibrous tissue even if the cell dimension and cell wall thickness occur in highly desirable characteristics. For the most part the bamboos appear to have a high ratio of parenchymas to fibres and vessels. 4.The basic density of bamboos was found to vary in different species showing in Table 2. This will be correlated with cell wall thickness as shown in Fig. 4. It also reflects more or less changes in fibre contents. The determination of basic density should be considered as one way for assessing wood quality for pulping. Although the increase in yield has been associated with increase in density, however, some species with lower basic density usually give pulp with higher over-all strength. The yield is only one factor but the behaviour of the fibres is much more important on the suitability of new species for pulping purposes. According to the results of the above mentioned examination 33 species of bamboos, as compared with one another as to thdr mean fibre length, cell wall thickness and basic density, can be classified in 4 groups: namely, 1st group No. 1. (Bambusa rigida) No. 2. (Bambusa sinospinosa) No. 3. (Schizostachyum pseudolima) No. 4. (Sinocalamus affinis) No. 5. (Schizostachyum hainanense) No. 6. (Bambusa lapidea) No. 7. (Phyllostachys bambusoides) No. 8. (Dendrocalamus strictus) No. 9. (Sinocalamus oldhami) No. 10. (Schizostachyum funghomii) No. 11. (Chimonobambusa utilis) No. 12. (Phyllostachys pubescens) No. 13. (Lingnania chungii). 2nd group No. 14. (Sinocalamus minor) No. 15. (Bambusa pervariabilis) No. 16. (Phyllostachys congesta) No. 17. (Semiarundinaria henryi) No. 18. (Lingnania cerosissima) No. 19. (Chimonobambusa quadrangularis) No. 20. (Phyllostachys angusta) No. 21. (Phyllostachys nigra var. henonis). 3rd group No. 22. (Sinocalamus latiflorus) No. 23. (Chimonobambusa mormurea) No. 24. (Bambusa textilis) No. 25. (Sinarundinaria nitida). 4th group No. 26. (Bambusa multiplex) No. 27. (Shibatea chinensis) No. 28. (Phyllostachys virdi-glaucescens) No. 29. (Phyllostachys anguta c. V. solidstem) No. 30. (Pleioblastus amarus) No. 31. (Pseudosasa amabilis) No. 32. (Sinocalamus distegius) No. 33. (Pseudosasa japonica). A total of 33 species representing 12 genera were reported. Among them representatives of 1st and 2nd groups appear to be the most promising in view of yielding high quality pulp, that is also said to be an important source of fibres. After all both the morphological studies and the determination of basic density should be considered to be most significant in indicating those species for the preparation of pulps in high yield and of good strength properties, however, they should not be regarded as the pulping and pulp evaluation studies.

It is said that Pinus massoniana Lamb, which growing in the Kwangtung province is of two forms, i.e., one possessing more resin and the other with less resin. In the present paper, both the wood structure and the physico-mechanical properties of the two form timbers which were collected from the northern part of the province have been preliminarily studied. They are about thirty years old. According to the wood anatomical characteristics, these forms may be distinguished as follows: the first form comparing with the second form has wider ring-width, lower late-wood percentage, thinner tracheid-wall thickness and larger lumen-width, shorter tracheid-length, more rays and more radial resin ducts, less in numbers of tangential wall pits on late-wood tracheids, shallowly dentate ray tracheids, and more window-like pits per cross-field. Above all, the ring width and the tracheid length are the salient features. Among the physico-mechanical properties of the two forms of timbers, only both the strength in tension parallel to the grain and the shearing strength parallel to the grain have reliable differences. Moreover, the strength index, the strength/weight ratio and the height-growth rate are higher in the second form than which in the first one. In comparison with the race from other localities, the Masson pine timbers grown in the northern part of Kwangtung are the strongest in the main strength properties.