61 
the shoots. The spores are evidently wind-borne and are thus 
transferred from diseased to healthy parts of the shoots. 
The hyphae of the fungus occur in abundance in the infected 
shoots and leaves; they are colourless when young and become 
darker in colour as they grow older, the old hyphae being of a dark- 
brown colour ; they are septate at frequent intervals and measure 
on the average 5-6 m in width. The hyphae are most frequently 
met with in the cortex and phloem, but sometimes they extend into 
the wood along the medullary rays. e tissues which are more 
especially affected are those which serve as channels for the 
conduction of elaborated food material. The resultant*effect of an 
attack of the disease is the diminution of the food material available 
for the growth of the plant. 
In the experiments which were conducted at Kew for the purpose 
of determining the mode of entrance of the fungus into the tissues 
and its variety of hosts the following’species were employed : 
Pinus sylvestris, P. Strobus, P. insignis, P. Pinaster, P. montana, 
Picea excelsa, Abies pectinata, and Larix europaea. The plants were 
three years old, and in each case three plants were infected and one 
kept as a control. 
Various attempts were made to infect the leaves and the younger 
and the older parts of the shoots by transferring the spores of the 
fungus to the unbroken surface in a drop of distilled water. The 
plants were kept in a greenhouse at a temperature of 75° F., and 
five attempts were made on each plant. The capacity for 
germination of the spores was previously tested by mounting them 
in water in a hanging-drop and germination was found to be active, 
taking place within 24 hours. All attempts to infect at an 
unbroken surface failed. 
By similar experiments it was found that infection could occur 
readily at a wound ; it was demonstrated that only a small wound, 
such as a puncture, was sufficient, the spores being transferred to 
a drop of water on the puncture. Positive results were obtained 
only with the species of Pinus ; repeated attempts failed to produce 
any infection of the species of Picea, Abies and Larix 
the nc following that of infection. My results showed that no 
