RECENT INVESTIGATIONS IN REGARD TO QUALITY OF TIMBER. 283 
always found in the portion comprising the Ist to the 30th rings, 
and steadily decreases as the section is followed towards its peri- 
phery. This variation in the sp. gr. of the wood from high and 
low class soils, doubtless stands in intimate relationship to the 
volume of the lumina of the cells. On poor soils growth is very 
slow in early youth, and therefore the cells are small and the wood 
is close-grained. Later on, when the shading of the ground is 
more complete, better growth results, the cells and their lumina 
becoming larger, On high-class soils growth is relatively faster 
in early youth, and slows down when crowding becomes severe. 
The close relationship, though in inverse proportion, between 
rate of growth and sp. gr. in trees of the same age grown on soils 
of equal quality, is well illustrated in the case of 20 selected trees 
30 years of age. Ten of these, from West Prussia, showed an 
average volume of 5:79 cubic feet and a sp. gr. of -505, while the 
other ten, from Saxony, averaged 27°96 cubic feet with a sp. gr. 
of -448. The slow-grown trees had thus a sp. gr. about 12 per 
cent. in excess of the others. 
The close relationship between the quantity of autumn wood 
and the sp. gr. is clearly shown in these investigations. With 
scarcely an exception, the highest sp. gr. for any section corre 
sponds with the highest percentage of autumn wood. There is, 
however, no general correspondence between ring-breadth and 
sp. gr., that is to say, a broad ring may or may not be lighter 
than a narrow ring, though, on the whole, it is no doubt lighter. 
The relative proportion of autumn wood to spring wood generally 
decreases as a stem is followed up, which partly accounts for the 
best wood being found in the bottom section. The figures for one 
tree may here be given :— 
Height from Rings formed Auonade breadth per cent. of Ring | 
Ground in between g Ring Hb occupied by | Sp. Gr. 
Metres. the Years. Twenty-fifths of | autumn Wood. 
an Inch, 
1 PO=PE-20 66 larson ‘511 
31-60 3°8 47°7 "530 
61-90 2°9 49°1 560 
8 0-30 9°3 23°7 434 
31-60 3°8 | Bye 477 
61-90 2°3 | 31°2 477 
In this connection Schwappach specifically states :— “Any 
influence, natural or cultural, that increases the percentage of 
