38 BULLETIN 1053, U. S. DEPARTMENT OF AGRICULTURE. 



nation, but excellently adapted to dissemination by insects or drip- 

 ping water. The practical application of these facts is obvious. If 

 secondary spores occur outside of artificial cultures, there is no place 

 more suitable for their formation than in the structures of wet oc- 

 cupancy referred to. In these structures, where conditions are moist, 

 there would be insects or animals, such as sow bugs and cockroaches, 

 and there is commonly dripping water, precipitation water upon cool 

 masonry, around cold-water pipes, etc. 



OCCURRENCE IN BUILDINGS OF THE SECONDARY SPORES OF 

 THE FUNGI STUDIED. 



The step following the demonstration that oidia can disseminate 

 fungi, such as Lenzites sepiaria and L. trdbea, is to prove that such 

 oidia occur naturally in buildings. The outstanding fact is that 

 many European writers have suggested the importance of the sec- 

 ondary spores in the economy of the fungus, if found naturally, and 

 that no one has yet reported such occurrences. The writer has little 

 information on the subject. The only secondary spores found in mills 

 are the chlamydospores on the mycelium overgrowing the gills of 

 fruit bodies of Lentinus lepideus (PI. V, fig. 6). These are formed 

 quite abundantly, but thus far nothing is known of their ability to 

 disseminate the fungus. The spores which the writer found were 

 on old fruit bodies, and tests as to their ability to germinate failed. 

 There is, of course, the possibility that freshly formed chlamydo- 

 spores may germinate, and, if so, they would disseminate the fungus 

 much as do the basidiospores which are overgrown and imprisoned 

 by the chlamydosporic mycelium. This means of dissemination 

 would appear to be not so efficient a method as by the basidiospores 

 which they replace, because the basidiospores should be lighter and 

 hence capable of wider dissemination. 



It is known that certain fungi do form superficial mycelium within 

 the structures referred to in these studies as well as out of doors. 

 Falck (15, p. 154) relates that the fruit-body-forming mycelium 

 (fruktiftkative Oberflachenmycel) of Lenzites sepiaria is found on 

 moist places on beams, and he states (15, p. 143) that it is capable 

 of producing oidia, although he has not reported the finding of these 

 oidia in buildings. The writer has examined some superficial myce- 

 lium of Lenzites sepiaria and L. trabea upon planks secured from 

 mill roofs, but the presence of oidia or chlamydospores as yet has not 

 been definitely established. 



SUMMARY. 



In textile and paper mills prevailing conditions of humidity and 

 temperature provide a favorable environment for the development 

 of wood-decaying fungi. Under such conditions poorer grades of 



