Nov. 3,1923 Five Molds and their Penetration into Wood 
223 
GOLD SOLUTIONS 
Of all the solutions used, c. p. gold chlorid in distilled water gave the 
most satisfactory results. The best differentiation was obtained with 
very dilute solutions (1 part gold chlorid to 2000 parts distilled water) in 
which the sections were allowed to stand for a considerable period, 24 
hours or more (PI. 2, B and C; PI. 3, B; and PI. 4). Greater contrast 
and quicker response were obtained in some cases by giving the sections 
a preliminary treatment with borax (sodium biborate) or with a 2 to 10 
per cent solution of sodium acid sulphite, or of sodium thiosulphate 
(photographic hypo). With the gold solutions the mycelium appears in 
various shades of purples and reds against a paler or more bluish back- 
ground. A very clear differentiation is given, even in the case of the 
very fine mycelial threads. Interesting differentiations in the various 
elements of the wood itself are brought out by this treatment (Cf. PI. 3, B). 
OTHER SOLUTIONS 
Other chlorids, including those of mercury, platinum, and palladium 
also were tried, but were found to be decidedly less effective than gold. 
selenium dioxid 
Some selenium dioxid crystals were obtained through the courtesy of 
Professor Victor Lenher, department of chemistry, University of Wis¬ 
consin. The wood was colored scarlet (especially if heated) by solutions 
of various concentrations, but no differentiation was obtained. 
EXTENT OF ATTACK OF MOLDS ON WOOD SPECIMENS 
ASPERGILLUS NIGER 
The culture of Aspergillus niger grew vigorously. It developed its 
characteristic black spores on the surface of the blocks, as is indicated in 
Plate 1, G. The individual test blocks, when removed from the culture 
flask, were found to be more or less discolored on the surface, chiefly by 
the dark, powdery spores of the mold. The ends especially, which were 
not smooth like the sides, were much affected. The sides showed slight 
discoloration, but the interior of the blocks, except for the growth in the 
pores or vessels, appeared to the naked eye about as clean as at the begin¬ 
ning of the test. The exterior of the oak blocks was more discolored 
than that of the spruce and aspen material. 
The mycelium of this mold was found chiefly in the vessel cavities. 
The hyphae developed abundantly in these open, readily accessible tubes 
and were chiefly confined to them, as is illustrated by Plate 2, C. Practi¬ 
cally no penetration through the thick cell walls was found. The hyphae 
were abundant in spruce (which has no vessels), but their course in this 
species was chiefly longitudinal in the tracheid cavities; there was a 
minimum number of crossings from cell to cell, and these appeared to be 
chiefly through the pits or thin areas in the cell walls. The diameters of 
the hyphae were larger near the surface of the wood than below. Little 
or no injury to the wood was apparent in the material. 
CERATOSTOMELLA sp. 
The blocks inoculated with Ceratostomella sp. did not show the char¬ 
acteristic bluing usually associated with its presence in nature. Other¬ 
wise, the development of the culture was normal. Some of the hyphae 
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