Abstract: Pseudosasa amabilis (McCl.) Keng f.,the Tonkin Cane,is a famous exported bamboo.The present paper deals with both variations in the mean fibre-lengths between the internodes and the distribution of fibre-lengths within the plant of three-year-old culm. All the macerated materials were selected from the outer part,i.e.,adjacent to the epidermis, the middle part and the inner part,respectively.These were taken from the middle of an inter- node along its diameter.Each part was consisted of two match-sized sticks,and was macerated and mounted on a slide.Total 615 slides were made.They were supplied from 205 internodes of 9 culms which had been collected from two slopes of the native place (Table 1).A report of the habitat of this Bamboo was quoted. The length of fibre was measured by projection with the aid of a graduated circular target (Fig.1;).All measurements and calculations were separated in regard to both different inter- nodes and parts. After studying the lengths of 24300 fibres which are distributed to the three parts from the Znd to the 19th internodes(Tables 2—5;Figs.2—3),some facts may be concluded as follows: 1)That the mean fibre-lengths between the internodes increase with the order of the internode upwards from the ground.When the fibre reaches its maximum length,it decreases its length with the internode order upwards further. According to the result of calculation,the increases of mean fibre-lengths of different parts from the 2nd to the 5th internodes generally are apparent.Before a given internode (i.e.,fibres of the outer part is at the 10th internode,those of the middle the 11th,and those of the inner the 13th),fibre-length tends to (or comparatively) increase wavely (or gradually).After this inter- node,the length tends to decrease,commonly wavely.However,fibre-length may slightly increase in the 17th internode.Beyond this internode,the length generally decreases apparendy.(Tables 2—3;Fig.2.) 2)That the increase or decrease of the length of an internode is similar to that of the fibre length,ie.,it varies with the order of the internode upwards.In other words,the increases of the internode lengths from the 2nd to the 5th internodes are correspondingly apparent.Next,the internode length gradually increases.After the 13th internode,the length decreases gradually. 3)That the variation in the fibre-length of the inner part comparatively is more similar to the variation in the length of the internode.This relation between fibre-length and internode-length seems not so closely as in the case of the fibre-length of the outer part,and,in terms,of the middle part.(Table 5.) 4)That the mean fibre-length of the outer part is longer than that of the middle and that of the inner.(i.e.,1995±25μ,1858±29μ,and 1687±27μ,respeetively.)Between the order of internodes,the increase or decrease of fibre-length of the outer part is more typical than the pheno- mena present in the middle and the inner parts (Fig.2). 5)That both variations in the diameter of an internode (here it is expressed as the diameter of the ring which taken from the lniddle of the internode) and in the thickness of the internode (here expressed as the wall thickness of the same ring) decrease with the order of the internode upwards.(Fig.2.) 6)That,therefore,the increase and decrease of the mean fibrelengths of different parts are affected by the factor of the internode length.And 7)That the distribution of fibre-lengths of three-year-old culm of Pseudosasa amabilis along the radii of the middle of the internodes examined,the fibres of the outer part are the longest,(1998± 445μ);those of the inner are the shortest,(1675±401μ);while those of the middle are the inter- mediate,(1851±409μ).(Table 4;Fig.3.)