436 
Williamson. — The Origin of ‘ Golden ’ Oak. 
of i*i6. Its optimum pH value is between 2 and 3, and its minimum is 8-2. 
(6) There is evidence that the fungus is capable of utilizing certain acids, such 
as malic, tartaric, citric, and gallic. Its growth on tannic acid is practically 
the same as on the control nutrient medium, showing tolerance of the acid 
but giving no evidence of utilization. (7) The yellow colour of the conidia 
is insoluble in ether, chloroform, alcohol, and water. These physiological 
characteristics are important in the consideration of the fungus in relation to 
the oak. 
E. CATENULATA IN THE WOOD. 
The cellulose acetate method (8) was the one usually employed in order 
to soften the oak and obtain sections with the fungus uninjured. Small 
cubes of the infected oak, at different stages after inoculation, or of the 
original specimen after soaking, were de-aerated under water. They were 
left in pure acetone for two hours, and then placed in a solution of cellulose 
acetate in acetone. After six to ten days these could be cut on the Jung 
sliding microtome. This time could be about halved if the tubes containing 
the blocks in the cellulose acetate were 
placed in an incubator at 40° C. Sections 
were cut about 10 p thick and placed in 
acetone to dissolve out the cellulose acetate, 
followed by alcohol to replace the acetone. 
After this they were stained, usually with 
a saturated aqueous solution of safranin 
followed by light green in clove oil. The 
fungal hyphae took up the light green 
very well. Another stain which proved 
useful was a slight variation on that recorded 
by E. E. Hubert ( 5 ) for staining fungi in 
wood. The sections were placed in Bismarck 
brown (2 per cent, in 70 per cent, alcohol) 
for about two minutes, washed with distilled 
water, dehydrated, and then left in a solu¬ 
tion of methyl violet in clove oil for three minutes. The violet stain was 
differentiated in clove oil followed by cedar oil and Canada balsam. 
It was found possible, after the use of cellulose acetate to soften the 
wood, to embed in paraffin, and cut with a Cambridge rocking microtome. 
The small blocks were transferred from cellulose acetate to acetone for a few 
hours, and then placed in 95 per cent, butyl alcohol as given by Mile 
Larbaud (6), after which the blocks were passed through two baths of pure 
butyl alcohol, to the second of which paraffin was added. Embedding 
followed the usual process, and sections were mounted and stained in the 
usual way. 
Text-fig. i. Longitudinal sec¬ 
tion of wood-vessel showing hyphae 
with globules of secretion and chains 
of conidia. x 290. 
