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Gliotoxin is shown to be a metabolic product of Trichoderma viride, and a semi‐continuous apparatus for its production is described. Ammonia nitrogen is preferable to nitrate nitrogen, but a wide range of carbon sources, and organic or inorganic sulphur sources, are suitable for gliotoxin production. No organic supplements to a glucose‐mineral medium have been found to affect gliotoxin production beneficially. Data are presented showing gliotoxin to be moderately toxic to a wide range of bacteria, actinomycetes and fungi. T. viride itself is resistant to its toxic effects. It shows fungicidal activity when applied as a dust to cereal seeds bearing various seed‐borne diseases, but is inferior to organomercury compounds for this purpose. Its value as a fungicide for control of plant or animal infections is reduced by the instability of aqueous solutions, except at low pH.

Gibberellic acid is a metabolic product of the fungus Gibberella fujikuroi, similar in physiological properties to the gibberellins described by Japanese investigators. Supplied in a nutrient solution to wheat plants growing in water culture, it causes increased growth of the shoots, as a result of increased length of stem internodes and leaves. The leaves are narrower and paler than those ot untreated plants. Under similar conditions pea seedlings develop much elongated stem internodes, but the leaves are little changed in size. These morphological responses are similar to those seen in etiolation.The total dry weight of both peas and wheat so treated is increased ; if shoots alone are considered the increase in dry weight is even greater ; the dry weight of roots is reduced, though this does not occur if the gibberellic acid is applied to the shoots in a lanolin paste. The increased dry weight is mainly attributable to increased carbon assimilation. Treated plants contain more soluble carbohydrate than controls, but this accounts only for a small part of the increased carboil assimilation. The increase in glucose content is particularly striking.Gibberellic acid is rapidly biologically degraded in soil. IntroductionA soil-borne fungus, Gibberella fujikuroi (Saw.) Wr. (conidial stage Fusarium m o d i f o r m eSheld.), is the cause of a disease of rice seedlings, not uncommon in Japan and other countries of the Far East, and recently found in Italy. A characteristic early symptom of the disease is elongation of the shoot, so that, in an infected crop, diseased plants are much taller than healthy ones, giving an impression that the crop has germinated unevenly. In the later stages of the disease fungal invasion causes considerable necrosis of basal tissues of the plant and the seedlings become weakly or die. Kurosawal showed in 1926 that the symptoms of overgrowth could be induced in rice seedlings by applying cell-free filtrates from liquid cultures of G. fujikuroi to the roots. This observation was confirmed and extended by other Japanese workers2-' shortly afterwards. The main features of the action established by this work were : (a) that though overgrowth of shoots 'was produced by culture filtrates, growth of roots was unaffected ; (b) that not only rice plants, but other plants, including dicotyledons as well as monocotyledons, responded by increased shoot growth ; (c) that the active material in culture filtrates could be adsorbed on charcoal and eluted by acetone or ether ; ( d ) that the increased height of plants was sometimes associated with an increase in dry weight, though more frequently dry weight was unaffected.An active material was isolated from culture filtrates in pure form by Yabuta & Hayashi,B which was named gibberellin A.e Another active material, gibberellin B, was also obtained, but gibberellin A was the main substance isolated. Its biological properties were described in a number of papers which will be referred to elsewhere in this paper. Gibberellin A produced overgrowth of seedlings ...