Add to ORKGEvaluation of nutrient availability in soils, and prediction of yield response to fertilization. C.A. Black 1 Effects of organic mercury compounds on enzymatic oxidation of malic acid. James L. Hilton and Frederick G. Smith 13 Fungus leaf spots of brome grass in Iowa. Lois H. Tiffany 21 The leguminosae of the north-central United States II. Hedysareae. Duane Isley 33 Growth of crappies, bluegill, and warmouth in Lake Ahquabi, Iowa. Richard C. Hennemuth 119 Effect of fluorescent and incandescent light on temperatures in photoperiodic chambers. S.C. Wiggans and R.H. Shaw 139 Life history of the black bullhead, Ameiurus melas (Rafinesque), of Clear Lake, Iowa. John L. Forney 14