Chow, Hamar & Udall (1972) reported that a water-soluble (`aqueous') fraction extracted from the needles of yellow pine (Pinus ponderosa) could disrupt fetal development of mice and some constituent of the pine needles was believed to be responsible for the activity. However, the aqueous fractions of pine needles harvested in the following 2 years induced little reproductive failure in mice. This inconsistency in activity raised doubts concerning the toxicity of the pine needles.
A preliminary study was undertaken to determine whether metabolites produced by fungi which we had observed on the pine needles could be the cause of the reproductive failure. Several pine needles were placed in the aqueous fraction. Fungi started to grow within 2 days of incubation at room temperature. After 2 weeks of growth, the