1912] Fred J. Seaver and Ernest D. Clark 425 



were very soon covered with a luxuriant web of mycelium of 

 Pyronema which produced its salmon-colored fruiting bodies and 

 then disappeared. This is another illustration of the fact that con- 

 ditions of media entirely unsuited for green plants may be highly 

 favorable to fungi. One should be careful not to speak of "toxic" 

 or "poisonous effects" unless the organism is mentioned to which 

 such reference is made. 



The cultural experiments just outlined show that heating soils 

 to temperatures above 120 seems to produce effects unfavorable 

 to the growth of oats, while heating to less than 120 , depending, 

 of course, upon the crop and soil used, seems to be slightly beneficial 

 or, at any rate, not definitely harmful. The harmful effects on 

 green plants and the beneficial effects on fungi seem to increase, 

 hand in hand, with the intensity of the heat. This may indicate 

 that both effects are due to the relative amounts of substances in 

 solution and not to their so-called harmful or beneficial nature. 

 This parallelism is so complete that it does not seem likely that the 

 effects of heating soils are mainly due to the destruction of living 

 organisms — the protozoa mentioned by Russell and Hutchinson or 

 the spores of harmful fungi according to Bolley. In other cultural 

 studies we made extracts of similar series of heated soils for chem- 

 ical analysis and for culture solutions in lupin experiments now to 

 be outlined. 



THE EFFECTS OF SOIL EXTRACTS UPON LUPIN SEEDLINGS 



After satisfying ourselves that strongly heated soils were dis- 

 tinctly harmful to the growth of oats upon them, we then used 

 extracts from series of soils heated to different temperatures for 

 equal periods of time as culture solutions for lupin seedlings. These 

 seedlings had been started in germinators filled with sphagnum moss 

 and the radicle allowed to reach a length of 3-5 cm. The seedlings 

 were placed in Jena beakers containing 200-300 c.c. of the extracts 

 to be studied. They were placed on glass rods in lots of four in 

 each extract after the manner described by True and Gies. 17 All 

 measurements are given in millimeters of growth in the designated 

 time and represent the average for four seedlings (Table 3). 



17 True and Gies : On the physiological action of some of the heavy metals 

 in mixed solutions. Bull. Torrey Botan. Club, 30, 390. 1903. 



