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subject of the present description was originally published by
Professor K u n z e as a Melancommm ; hut if the distinction
is to hold good between the two genera, as defined by N e e s
and F r i e s , it must belong to Didymosporium, where, indeed,
it has been already placed by L i n k , on account of its didymous
sporidia. The two genera are evidently so nearly related, that
it is doubtful whether they will be both retained when the species
are more accurately investigated.
Fig. 1. D. betulimim, on birch-bark; natural size. Fig. 2 . A section o f two
plants, one o f them exuding its sporidia through the epidermis. Fig. 3. A horizontal
section o f a plant, shewing the black mass o f sporidia, surrounding
the spurious receptacle. Fig. 4. Sporidia; magnified.
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