Ovule number in Pisum was shown to be controlled by a simple, additive genetic system, with perhaps as few as three loci governing the entire range. An association was demonstrated between the Bt locus (conditioning the shape of the pod apex) and the number of ovules per ovary. The nature of the association, linkage or pleiotropy, remains unsettled.

Panicle weight components (i.e., number of branch whorls per panicle, number of branches per whorl, number of grains per branch and grain weight) and rachis morphology were analyzed under different soil fertility and plant population treatments. High soil fertility and low plant competition increased the 1000-grain weight and number of grains per panicle. The latter component was affected by soil fertility through the number of branches per whorl and the number of grains per branch, and by plant competition through the number of whorls per panicle and the number of grains per branch. Higher soil fertility and lower plant competition promoted a longer panicle through the increase in rachis internode length and number of internodes, respectively. The degree of contribution of some components to the number of grains per panicle was not always equal throughout the length of the panicle. A negative correlation, which became stronger as the number of grains per panicle increased, was found between weight of grain and number of grains per branch. Intra-panicle competition between these components was suggested.

Markov processes, despite their limitations, are becoming more widely used as a method of making projections of size and income distributions. The number of potential entrants to an industry or a population assumed in an analysis has an important effect on both short‐run projections and equilibrium solutions. The number of potential entrants is not a passive variable, as has often been said or implied. Through the use of changes in the number and size of dairy farms in New York State as an example, alternative projections in the short run are presented for different assumptions about the number of potential entrants. The general case is developed algebraically for the effect of the number of potential entrants assumed (N) on the equilibrium solution for the vector t.

To test the constancy and predictive value for maturity classification of number of leaves developed on the main stalk in maize, 21 double crosses were studied in three replicated trials. The plantings were made on May 15, 1965, in Illinois and on September 10 and November 22, 1965, in lqorida. Eighteen of the hybrids were commercial dents selected to represent the range of kinds and maturities grown in the United States and Canada. Three later maturity experimental flint/dent double crosses were added to extend the range of maturities studied. Highly significant positive correlations were obtained between number of leaves per hybrid and days to anthesis in each planting. Leaves per plant were fewer in the winter plantings than in the summer. Fewer days were required for anthesis in the September planting than in the other two. Highly significant positive correlations were obtained among plantings for number of leaves per hybrid and for number of days from planting to anthesis. Number of leaves per hybrid was in these trials a highly reliable index of maturity class.

Viability and oviposition of the parasitic wasp Nasonia vitripennis on its host Phaenicia sericata at various parasite—host densities were analyzed. As the parasite density becomes excessive, an increasing portion of the progeny is reduced. These density—dependent reduction mechanisms are: retention of eggs if a sufficient number of hosts is not available; death and decomposition of superparasitized host pupae resulting in death of the parasite larvae; food shortage within the host leading to parasite mortality shorty before and during metamorphosis; reduced longevity and fecundity of viable female offspring from superparasitized hosts and a decreasing portion of female progeny as the parasite number on a given host supply increases. This change in sex ratio is relatively independent of the number of eggs laid per parasite female or per host pupa. It is mainly determined by the number of simultaneously ovipositing females: the more dense the ovipositing females, the less fertilized eggs they produce. Two categories of density—dependent regulation mechanisms are distinguished: behavioural and pathological mechanisms. The significance of the two categories for the existence of a theoretical population equilibrium on the one hand and for a real equilibrium on the other hand is discussed.

Young free—trailed bats, Tadarida brasiliensis mexicana, fall to the floor of nursey caves where they are eaten by beetles and predators. The number of young falling is correlated with the number of young in the cave and the bat's age. During the first two months of life there is a loss of 1.3% of the population. Ths mortality is lower than for the adults over a comparable period.