430 SOIL FUNGI 



and Koning (1902) placed a fragment of humus in a small vessel 

 containing 1 ml of sterilized water. After the humus has been 

 thoroughly triturated, a platinum loopful of suspension was intro- 

 duced into 10 ml of sterilized water. A small quantity of this di- 

 lute suspension was then poured upon the surface of poured plates 

 of media, consisting of agar 1.5%, gelatin 10 o/ o , and sucrose 2%, 

 with an added quantity of wort. 



HaQ-em (1910) sprinkled small amounts of soil on the surface 

 of poured plates in attempts to isolate Alucorales. By repeated 

 transfer of mycelium and spores to new substrates he secured pure 

 cultures. Lendner (1908) employed tubes or flasks of wort 

 gelatin or of moist bread on which small amounts of soil were 

 planted. Several other workers have used a filtrate of soil, sus- 

 pended in water for 24 hours, to enrich the media. Matters in- 

 volving media and methods of sampling and of isolating soil fungi 

 are discussed in an outline bv Waksman and Fred (1922). They 

 recommend the use of sodium albuminate agar, sodium caseinate 

 agar, or soil-extract agar and gelatin. 



Since fungi are tolerant of acid substrates, whereas bacteria and 

 actinomycetes grow best on neutral or alkaline media, a reaction 

 of pH 4.0 to 5.0 is preferable in the isolation of fungi. 



Conn (1922) proposed the use of a technique by means of which 

 the presence of fungus hvphae in soils could be demonstrated by 

 direct microscopic examination. 



In isolating "water molds," a small quantity of soil, along with 

 some sterilized water, is first placed in a Petri dish, and then 

 boiled hemp seeds are introduced as "bait." Many workers, be- 

 ginning with Harvey (1925), have employed this technique. 



Kinds of fungi isolatfd. Opinion was divided among earlier 

 students on whether funQ-i are normal inhabitants of the soil. 

 The weight of evidence, however, has gradually favored the ex- 

 istence of a true fungus flora of the soil. The isolations of 

 Adametz (1886) yielded 11 species of fungi, among which were 

 Aspergillus gluteus, Penicillium glaucum, Mac or vmcedo, M. 

 raceinosus, and M. stolonifer. These species have been quite com- 

 monly found by all whose interest has centered on the problem 

 of kinds of soil fungi. These investigators have included Oude- 

 man and Koning (1902), Lendner (1908), Hagem (1910), Beck- 

 with (1911), Dale (1912, 1914), Jensen (1912)" Goddard (1913), 

 Werkenthin (1916), Paine (1927), Gilman and Abbott (1927), 



