[VoL. 3 
448 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
Bacillus amylovorus and Rhizoctonia is hardly acceptable 
without adequate specific data for each of the organisms 
concerned. 
Speaking of the fungous diseases in the tropics, Westerdijk 
(215) says: 
“The heavy rainfalls, combined with the abundant transpira- 
tion—owing to the intense heat, must cause a high water-content 
and a small air-content, of the wood-vessels of the trees, thereby 
making a substratum poor in air. This fact, combined with 
the high temperature, would explain the rare occurrence of 
LOTION and other wood-destroying fungi in the 
tropics 
A certain balance between water and oxygen is necessary, 
and this varies according to the specificity of the organism. 
Just what percentage of water in the cell walls and oxygen in 
the lumen of the wood fibres are necessary for the entrance 
of fungi are undetermined factors, but we know that both are 
necessary. Well-seasoned wood is very durable as long as it 
is kept dry. On the other hand, upon damp wood spores of 
fungi germinate and penetrate readily. In speaking of Len- 
gites spp. Falck (209, р. 223) says that the spores germinate 
with every rain, then there forms a small colony from which 
hyphae enter the wood substance. In such colonies are found 
the typical medallion mycelium which endures dry periods, 
and which after a thorough saturation with water is again 
able to continue its life activities undisturbed. 
Wehmer (714) found that bits of mycelium of Merulius 
lacrymans transferred to air-dried blocks would not grow at 
room or cellar humidity. When the blocks were well saturated 
with water better results were obtained for mycelial growth, 
but decay was not evident in all cases. As decay by Merulius 
spreads the moisture content increases, decayed wood showing 
25 per cent hygroscopic water in damp air, where sound pine 
holds but 15 per cent. 
During the course of my work with Lenzites grown on pine 
blocks some interesting facts were noted concerning the 
growth and decay as they were influenced by the water and 
oxygen content of the wood. Blocks which were sterilized 
