On Polyporus squamosus Huds. 275 
of germ tubes. The spores are thus able to retain their power of 
germination for a considerable time under laboratory conditions. 
( b ). Germination on wood. On blocks of Sycamore and Horse 
Chestnut wood, Buller (6, p. 116) found that few spores germinated 
and penetration failed. 
Since cultures had been raised from spores on wood, it was 
obvious that germination and penetration had taken place and in 
order to observe this the following method was employed. Slips of 
wood, about 12 mm. square were placed in small tubes on damp 
cotton wool and sterilised. Fresh spores were collected and a little 
heap was placed at the centre of each slip, and these tubes were 
left in a damp atmosphere. 
They were set up on November 27, 1912. On December 3, a 
fair proportion of the spores was germinating, and little groups of 
tangled hyphae were present, formed by the germination of a number 
of spores close together, more especially among those spores which 
had been in direct contact with the wood. On December 7 the 
spores were germinating fairly freely, but apparently with some 
irregularity, and tangled hyphae of considerable length occurred. 
It did not appear, however, that any penetration of the wood had 
taken place. These cultures were re-examined on January 13, 1913, 
and were still pure. On examining a block under the low power of 
the microscope, the hyphae could be seen as fine lines stretching 
from the heap of spores in abundance, and then apparently 
penetrating the surface of the wood. Many of the spores which 
were not in contact with the wood had failed to germinate. 
On cutting sections of the blocks thus infected, near the region 
of the heap of spores, the hyphae were seen to have penetrated the 
vessels and other elements of the wood. As soon as the hyphae 
entered the wood, they followed more especially a longitudinal 
direction and were often present in large numbers in the vessels at 
some distance from the point of inoculation. 
This appears to explain the tardy appearance of the mycelium 
on the wood blocks in tube culture. The spores germinate quite 
slowly, and instead of forming a layer over the surface of the wood, 
they at once make their way into the tissues. Only after some 
time does the mycelium on the surface grow enough to be obvious. 
III. The Destruction of Wood. 
Buller has described the destruction of the wood of Acer by 
the fungus in nature. The hyphae penetrate all the wood cells and 
delignify them. The fibres between the spring elements succumb 
