A review of septate microsporangia in vascular plants. Nels R. Lersten. 487

Genetic effects of population size n the reproduction of two heterogeneous maize populations. Eliud Omolo and W.A. Russell. 499

Manipulation of crossing over in Zea Mays L. by Actinomycin D¹. James J. Mock. 513

Special meteorological data needs or agriculture. R.H. Shaw. 529

Age, growth and condition of black crappie Pomoxis nigromaculatus (Le sueur), in Lewis and Clark Lake, South Dakota, 1954 to 1967. C.J. Vanderpuye and K.D. Carlander. 541

Life history of red shiners, Notropis lutrensis, in the Skunk River, central Iowa. K.D. Laser an K.D. Carlander. 557

Influence of plant height, row width, and plant population on grain yield and yield component associations in grain sorghum. R.E. Atkins and Ricardo Martinez. 563

Change in genetic variance for seven plant and ear traits after four cycles of reciprocal recurrent selection for yield in maize. Arnel R. Hallauer. 575

Carbohydrate metabolism an respiratory activity of soybean seedlings. Abdul H. Wahab and J.S. Burris. 595

Duration of stigma receptivity in cytoplasmic-genic male-sterile grain sorghums. R.E. Atkins. 607

A comparison of soil and air temperatures in the spring at Ames, Iowa. R.H. Shaw. 613