SOIL FUNGI 257 



Wool is made up primarily of proteins whereas cotton is made up 

 of cellulose. Species of Alternaria, Stemphylium, Oospora and Peni- 

 cillium have been found by Prindle ^^ to be capable of having dele- 

 terious effects on wool fibers. Species of Trichoderma, Cephalo- 

 thecium, Dematium, Fusarium, and Aspergillus are some of the 

 molds which can alter the structure of wool. 



Molds can be used in the aerobic retting of flax. After being cut 

 the flax plants are spread out on the ground during the autumn and 

 winter in mild climates. Various molds attack the more available 

 compounds. The bast fibers, largely cellulose in nature, are less 

 easily available to most molds than are the pectins, hemicelluloses, 

 proteins, and starch. When the retting process is complete the bast 

 fibers can be easily separated. The crude fibers are then washed, 

 combed, and prepared for spinning. There is said to be less danger 

 of the cellulose fibers being attacked in the aerobic retting process 

 than in the anaerobic method, whereby the flax is immersed in 

 streams and the retting (a Middle English word for soaking) is 

 carried out by anaerobic bacteria. 



For further information, the reader is referred to Thaysen and 

 Bunker ''^ for an excellent discussion of mildewing in cotton goods 

 and also to Prescott and Dunn.** 



Although they are not the greatest source of economic loss, fila- 

 mentous fungi may render wood less valuable for certain purposes. 

 Species of Phialophora, Alternaria, Fusarium, Penicillium, Asper- 

 gillus, Cladosporium, Rhizopus, and others may produce stains or 

 discolorations on lumber. The stains may be due to the color 

 forme^ in the mycelium of the molds, to soluble pigments secreted 

 by the molds, or to chemical reactions between enzymes or other 

 compounds formed by molds and wood. Drying wood, or sub- 

 mergence in water, or chemically treating wood are measures that 

 are taken to prevent discolorations due to the filamentous fungi. 

 The fungi capable of disintegrating and destroying wood are, of 

 course, not always harmful. By destroying wood and other cellulosic 

 materials and thus returning organic substances back to the soil the 

 molds play an important, and beneficial, role in the economy of 

 nature. 



SOIL FUNGI 



The mold flora of soils have been studied extensively by a host of 

 workers since 1886. The large number of colonies and the varied 

 flora which appear when soil is plated out in acidified agar media 



