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 BOTANY the succeeding night it exhibited unusual activity. It continued in a more or less motile state for several weeks, when it matured and formed its sporangia. Some species pass the plasmodium-stage in the interior of decayed tree-roots or logs, and do not make their appearance till they emerge for the purpose of forming their fruits. Hence very little is known of their habits in the motile condition. On one occasion, in a wood near Harpenden, Herts, a decayed tree-root, quite a foot in diameter, was being examined for these organisms. In the centre the woody fibres were found to be saturated with plasmodium which when matured proved to be that of Hemiarcyria clavata. The sequence of changes in the life-cycle of the Mycetozoa is as follows : spore the distributive stage ; myxamaba and plasmodium the motile and assimilating stages ; sporangium the fruiting stage, the spores of which, when distributed, enable the cycle to recommence. Classification. The grouping and arrangement of the genera and species are based upon the characters and contents of the mature sporangia. The two principal divisions are those in which (a) the spores are de- veloped on the outside of the sporophores, and (b) those in which the spores are developed inside the sporangia. In the first division there is only one genus known, but in the second the genera are numerous. These are further divided according to the colours of the spores, the first cohort including those in which they are violet or violet-brown, and the second those in which the spores are variously coloured but never violet. The further subdivisions are based upon the presence or absence of lime in the walls of the sporangia, and also upon the characters of the capillitium when this is present. Distribution in Herts. As wind is the principal agent in the dis- persal of the spores of the Mycetozoa, it is obvious that most of the species must have a wide geographical distribution. This renders it highly improbable that any form would be confined to so limited an area as an English county, or even to the British Islands. The subjoined list of those which have been recorded for Hertford- shire, though by no means exhaustive, will give a fair idea of what forms the county would furnish to a local investigator. There are a few species deserving special notice, amongst which is Eadhamia nitens. This until a few years ago had not been recorded for any locality outside England. It is now known to occur in Ceylon and Antigua. Hertfordshire furnished the first-known British record of the plasmo- dium-stage of this species. The first two British localities for which Physarum citrinum was re- corded are Caddington and Welwyn, both in Herts. It has recently been found in Scotland, and is known to occur also in Germany ana Venezuela. Eadhamia ovispora has recently (1900) been found in Herts, the only previous British records being for the adjoining counties of Beds and Bucks. 79