Summary The frequency and intensity of vesicular‐arbuscular mycorrhizas in the species of a Molinietum coeruleae association was studied during the vegetative period. From the total number of fifty‐five species in the association only nine species were nonmycorrhizal. There was dependence of the frequency of entry points on the root depth and the vegetative season. The ground water table was relatively stable during the year and it did not exert strong direct influence on the intensity of mycorrhizal infection.

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SUMMARYThree subtypes of mycorrhizas, sensu Dominik (1955), were found on roots of Alnus viridis growing in New Zealand. Roots with 60% of their rootlets mycorrhizal absorbed phosphate five times as rapidly as non-mycorrhizal roots. Root nodules appear unable to absorb labelled phosphorus actively from externally supplied solution.

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