Eleven sugi cultivars in 20-year-old stands were sampled to quantify the tracheid lengths for juvenile wood and mature wood. Tracheid lengths of latewood were estimated from macerated tissue in every ring at the breast height of three to five trees in each cultivar. Tracheid lengths of every cultivars were initially short near the pith and increased outwards within about 15 rings from the pith, as shown in Fig.1. The result was that the tracheid length of the 16th ring was regarded as the representative value of tracheid length in mature wood. There were high correlations between tracheid lengths of juvenile wood and the tracheid length of the 16th ring from the pith, and the decision coefficients for correlations were shown in Fig.2 and Fig.3. However Figs.4 and 5 show that the plots of rings near the pith for cv. obiaka and cv. hinode deviate from the regression lines, and the tracheid lengths of these rings may be unsuitable for predicting the tracheid length in mature wood. In the 8th ring from the pith, there was no cultivar deviated markedly from the regression line of the tracheid length of the 16th ring on tracheid length of a given ring in juvenile wood as shown in Fig.9.スギ11品種の胸高部位円板を用いて, 未成熟材仮道管長から成熟材仮道管長を予測できるか否かを検討した. この検討に先立ち, 未成熟材から成熟材への移行時期を調べたところ, いずれの品種でも, 髄から15年輪目以降を成熟材とみなせた. そこで, 成熟材仮道管長として髄から16年輪目の仮道管長を採用した. 未成熟材の仮道管長と成熟材の仮道管長との聞に, 極めて高い相関関係が存在することが明らかになった. しかし, 髄近くの年輪では, 両者の関係を表す回帰直線から大きくはずれる品種が観察され, 年輪数の増加にともなう仮道管の伸長率に, 品種間で違いがみられた. このことは, 髄付近の年輪から成熟材の仮道管長を予測するとき, 重要な留意点と位置づけられねばならないであろう. なお, 髄からの年輪数が増加し, 8年輪目以降の年輪では, 回帰直線から大きくずれる品種は認められず, 成熟材の仮道管長を精度良く予測できるとみなすことができた
