[Vor. 5 
110 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
ing the strength of southern pine structural timbers based on 
these various investigations were proposed. In general, these 
tests showed that as the density inereases, the strength also 
inereases in a uniform manner, and the density ean be esti- 
mated by making use of the proportion of summer wood to 
spring wood in the annual rings. As the density is dependent 
on the summer wood, the percentage of summer wood is an 
index of weight and strength, and is an important guide in 
judging the quality of timber, independent of any defects it 
may contain. 'Tests made on pieces of summer wood and 
spring wood whittled out separately from broad rings of 
loblolly pine show that the strength and density of the sum- 
mer wood is very close to double that of the spring wood. 
Thus there is a definite relation between strength and density 
of pine timbers. 
In a recent paper the writer! reported results of experi- 
ments in which some important physical properties of 
southern pine woods were correlated with the decay induced 
by Leneites saepiaria. Some of these results show that the 
specifie gravity (density) of the wood materially influenees 
resistance to decay of the heart-wood, the more dense pieces 
being more durable. By the correlation of the function 
which specific gravity of wood has thus been shown to play 
in its strength and durability, one would naturally conclude 
that when a timber possesses properties to make it strong, 
the chances are that it will be correspondingly durable. Al- 
though such inferenees might be made, it was thought well 
to report the results of studies made on the resistanee to 
fungous decay of timbers which had actually been tested for 
strength. The results of these experiments are reported 
below. 
Метноов or EXPERIMENTATION 
Twelve samples each of longleaf pine (Pinus palustris) 
and shortleaf pine (Pinus echinata) were procured, the long- 
leaf pine from the Industrial Lumber Company, Elizabeth, 
1 Zeller, S. M. Studies in the physiology of the fungi. III. Physical prop- 
erties of wood in relation to decay induced by Lenzites saepiaria Fries. Ann. 
Мо. Bot. Gard, 4: 93-164. pl. 9-13. f. 1. Charts I-XI. 1917. 
