FUNCTION OF MENTZELIA NUDA (LOASACEAE) POSTFLORAL NECTARIES IN SEED DEFENSE

Mentzelia nuda is a coarse, short-lived perennial of the High Plains of North America. The flowers secrete nectar which serves as an attractant for pollinating bees. Postfloral nectar secretion attracts ants whose presence significantly enhances seed set. This is the first demonstration of advantage to postflowering activity of a floral nectary.     

Convergence of the age structure: Applications of the projective metric

This paper states necessary and sufficient conditions for the convergence of the age structure (in a discrete time, one-sex model of population growth); it also contains a new and simple proof of the weak ergodic theorem of stable population theory. The main tool used to attain these results is Hilbert's notion of the projective metric. This metric provides a way of defining the distance between positive vectors in $\text{R}$ⁿ which has two important features: First, the distance between any two positive vectors depends only on the rays on which the vectors lie; and, second, positive matrices act as contractions in this metric.     

Oral, osmotic minipump, and intramuscular administration to sheep of the Veratrum alkaloid cyclopamine

Logistic and biologic aspects of three separate means of administration of cyclopamine for experimental induction of terata or embryonic death in sheep were examined. Oral capsule administration of crystalline cyclopamine is logistically simple and biologically effective, but costly in terms of amount of compound required. Embryos were affected in five of seven ewes dosed cyclopamine orally at higher levels (four nonpregnant and one with cyclopia). Intramuscular administration of cyclopamine dissolved in ethanol was logistically simple but without biologic effect at levels tested. Three of three treated ewes had normal offspring. Osmotic minipump administration of powdered cyclopamine suspended in propylene glycol was logistically unsatisfactory with serious delivery complications. Osmotic minipump administration of cyclopamine dissolved in ethanol was logistically very satisfactory, and one ewe among three treated animals was nonpregnant at term. There were no nonpregnant ewes nor deformed offspring in 17 controls.