- .*>/! ,i if? « 
FIVE MOLDS AND THEIR PENETRATION INTO WOOD 1 
By Eloisb Gbrry 1 
Microscopisi, Forest Products Laboratory , Forest Service, United States Department 
of Agriculture 
INTRODUCTION 
During the war the necessity for shipping, kiln-drying, and otherwise 
handling green wood which was, destined for special and exacting uses, 
such as the construction of airplane parts or artillery equipment, caused 
special consideration to be given to the possible effects of molds develop¬ 
ing upon such material. (Sr loads of green lumber, for instance, often 
molded heavily in transit; again, thick mats of mold developed at the 
beginning of chy-kiln runs under the favorable conditions offered by the 
relatively low temperatures, and the high humidities used. Hence the 
•question was repeatedly in the minds of inspectors and others responsi¬ 
ble for the use of the wood, as to whether the molds produced more 
damage than the frequently obvious superficial discoloration. 
The following study was made at the Forest Products Laboratory in 
order to determine, as far as it was possible to do so by the use of labora¬ 
tory cultures and with the aid of the microscope, the extent of the pene¬ 
tration of common molds into such woods. This work was begun in June, 
1918, with some preliminary examinations of the effects of molds on 
wood. These showed no significant penetration of the cell walls. The 
results here presented were obtained from a set of pure cultures prepared 
in June, 1919. These grew from that date until May, 1921, when they 
began to show signs of drying out (PI. 1, D. E. F, and I). 
SPECIES OF WOOD 
Four species of wood were selected for this study: Sitka spruce (Picea 
sitchensis (Bong.) Trautv. and Mayer), a wood much used in airplanes, 
cow oak {Quercus michauxii Nutt.), a white oak, and a commercial red 
oak (j Quercus sp.) used for propellers and for artillery wheels, and aspen 
{Popubus tremuloides Michx.), selected because it is a wood easily attacked 
by fungi. 
Test blocks of these woods were cut and planed to a size of ^ X K X 
13^ inches. All of the material was sapwood, with the exception of a 
little heartwood on the edge of some of the spruce blocks. Samples of 
all the species were examined microscopically and found to be free from 
fungus hyphae before the blocks were prepared. Since the material 
1 Accepted for publication July io, 1923. A microscopicstudy of Penicillrum drvaricatum. Monilia sito- 
phila, Aspergillus niger, Ceratostomella sp. and an unidentified form (No. 712X8-X), grown for two years in 
flask cultures on Hocks of aspen, Sitka spruce, white oak, and red oak respectively. 
* Considerable assistance and many helpful suggestions were given in the course of the investigation by 
the members of the Laboratory of Forest Pathology of the Bureau of Plant Industry at Madison, Wis. 
The writer wishes particularly to acknowledge the help given in obtaining the cultures used, by Dr. C. J. 
Humphrey, Dr. C. Audrey Rickards, and Mrs. R. Lynn waiter. Helpful criticism and information on 
the use of special stains were also given by Dr. R. H. Colley and Dr. B. B. Hubert. ( In determining the 
extent of the penetration of the molds, at the end of the test, some experiments in differential staining to 
facilitate observation and photomicrographing were made. In this work the suggestions and the advice of 
Dr. M. B. Diemer, Chemist in Forest Products, were of great assistance. For this help, as well as for that 
given in making the photographs of the cultures and the photomicrographs, the writer wishes to express 
grateful appreciation to Dr. Diemer. 
Journal of Agricultural Research, 
Washington, D. C. 
ahg 
(219) 
Vol. XXVI, No. 5. 
Nov. 3,1923. 
Key No. F-10. 
