542 EXPERIMENT STATION RECORD. 



When the iniiiiimim of illumination, parallel rays, was studied it was found 

 that the carhoii dioxid assimilation increased with the increase in temperature. 

 Where the illumination was at 45°, which corresponds with average illumina- 

 tion, the increase was regular and the temperature rose until an optimum was 

 reached, after which the decomposition fell ofE more rapidly for the tolerant 

 than for the intolerant species. Similar results were ohtained when the leaves 

 were illuminated vertically, the decrease beyond the optimum falling more 

 rapidly than when less illuminated. 



Sunnuarizing his investigations, the author claims that under the conditions 

 of his experiments heat and light facilitate carbon dioxid decomposition, that 

 there is an optimum for each beyond which the assimilative energy diminishes, 

 and that the diminution in assimilation of carbon dioxid takes place more 

 rapidly with tolerant species than with those intolerant to shade. 



Temperature and toxic action, C. Brooks {Bat. Gax., 42 (1906), No. 5, pp. 

 359-375, dgms. 33). — A report is given of experiments with a numl)er of species 

 of fungi to determine the modifying effect of temperature on the toxic proper- 

 ties of certain chemicals as shown by the effect of these substances on germina- 

 tion and growth. The chemicals tested were nitric acid, sulphuric acid, and 

 a solution of copper sulphate, and the fungi employed were Botrytis vulgaris, 

 Monilia fnictUjcna, Stcrigvnitocijstis nigra, Miicor nnicedo, and PenicilUum 

 glaucum. The first two of these fungi are usually considered parasitic and 

 have a relatively low optinunn temperature, while the last three are saprophytes 

 and grow well at temperatures considerably above the optimum for the first two. 



It was found that in most cases the deleterious action of the toxic agent 

 increased rapidly with the rise in temperature, although there were marked 

 differences in the various fungi noted. There was a decided drop in the germi- 

 nation curves for Botrytis and Monilia between 5° and 10°. With PenicilUum 

 the fall came either between 10° and 15° or between 15° and 20°, while with 

 Mucor and Sterigmatocystis the downward curves began at 15° or 20°. There 

 was also found a remarkable agreement in the minimum temperature for the 

 germination of a particular fungus under certain conditions and the location of 

 the fall in the germination curve. In all cases the injurious effects were least at 

 the optimum temperature for the germination of the fungus, as shown from 

 check cultures to determine the rate of germination and development. 



Taking the total growth as a standard, the injurious effects of the toxic 

 agents decreased with the rise of temperature. This decrease is considered as 

 the result of approaching the optimum for the fungus rather than a mere 

 temperature effect, and the effects produced by the three chemicals were 

 widely different. The injury resulting from the (•()i>per sulphate solutions was 

 not as great, comparatively, at 15° as at 20°, while this was true of neither 

 of the acids. Sulphuric acid checked growth at the lower temperatures, but 

 in no case served as a strong stimulating agent. Nitric acid gave similar inju- 

 rious effects, but at the higher temperatures served as a remarkalile stimulus. 



Investigations on the effect of soil sterilization on tlie development of 

 plants, C. ScnuLZE (LaiKlir. Vers. Stut., 65 (1906), No. 1-2, pp. ISl-l'il, pis. 

 .'/). — In connection with previous studies (E. S. R., 18, p. 841) some effects of 

 soil sterilization on the growth of plants vi'ere observed, and the author has 

 since carried on experiments to determine the relation between soil sterilization 

 and development of plants. 



Pot experiments with field, meadow, and garden soils were made, the plants 

 used being oats, mustard, jieas. I)uckwheat, and grasses. To each pot a 

 nitrogen-free chemical fertilizer was added, which contained phosphoric acid, 

 dil>asic calcium phosphate, dibasic potassium phosphate, and magnesium sul- 

 XJhate. One pot of each series was untreated, one sterilized for an hour at 



