Wm. T. Penfound

Effects of Denudation on the Productivity of Grassland

Denudation (close mowing and removal of mulch) of ungrazed prairie and ungrazed cropland plots near Norman, Oklahoma, did not result in significant change in composition, but increased the biomass in both the priarie and cropland during the growing season. Total biomass in all plots was low in February—March, increased to a maximum in late July, and declined rapidly thereafter. Although 115 species were sampled, only the following six species contributed significantly to the total biomass: Andropogon gerardi, Panicum virgatum, Sorghastrum nutans, Andropogon scoparius, Leptoloma cognatum, and Panicum scribnerianum. Average daily productivity was very low in February—March, moderate in April, relatively high and approximately equal in May, June, and July, and negative in August and September. The cumulative productivity was moderate for April, approximately equal but relatively high during May, June, and July, but declined rapidly thereafter. The terminal standing crop of living material (early September) w...

Effects of Fencing and Plowing on Plant Succession in a Revegetating Field.

FIXBER, AND D. R. CORNELIUS. 1947. cessing grass seed. Agron. Jour. 45: RONEY, J. N. 1949. Bermuda grass seed Seed for regrassing great plains areas. 389-391. insects in Arizona. Jour. Econ. Ent. USDA Farmers Bull. 1985. RIEGEL, D. A. 1940. A study of the 42: 555. JONES, MEL,VIN D., AND L. C. NEWELL. variations in the growth of blue grama STITT, R. E. 1954. Seed production of 1946. Pollination cycles a,nd pollen grass from seed produced in various Russian wildrye. Agron. Jour. 46: 171dispersal in relation to grass improvesections of the Great Plains region. 175. ment. Nebr. Agric. Exp. Sta. Res. Bull. Trans. Kansas Acad. Sci. 43: 16-84. WOLFF, SIMON, E. 1951. Harvesting and 148. RIHERD, PAUL T. 1954. Thrips a limitcleaning grass and legume seed in the KNEEBONE:, W. R., AND H. W. BROWN. ing factor in grass seed production. western gulf region. USDA Agricul1953. A modified hammermill for proJour. Econ. Ent. 47: 709-710. ture Handbook No. 24. SEED PRODUCTION 21

The relation of plants to public health

In addition to furnishing clothing, food and shelter—the basic necessities of life—plants, in their utilization by man, have also furnished problems of public health in their production of alcohol, narcotics, allergies, poisons and specific human diseases.