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SOUTH AFRICAN PEEISPOEIACEAE. 
By Ethel M. Doidge. 
(With seven Text-figures). 
(Read May 19, 1920.) 
VI. The Haustoria of the Genera Meliola and Irene. 
The gfenus Meliola has received considerable attention from systematists, 
and is much studied from the taxonomic point of view by collectors and 
students of tropical and sub-tropical fungi. Comparatively little, however, 
is known of their method of nutrition or of their relation to the forest trees 
and shrubs, on whose leaves and shoots they are chiefly found. This is 
possibly due to the fact that until recent years these fungi were for the 
most part described by workers in Europe, who only had at their disposal 
scanty material sent to them by collectors in the Tropics. 
The earlier workers, such as Bornet (1) and Gaillard (2), stated that the 
lesions which one sometimes observes on leaves on which these fungi grow 
are due to the action of numerous mites, of which one often finds the 
remains. G-aillard even states that he has satisfied himself by examining 
numerous sections that the vegetation of the Meliolas is entirely superficial, 
and does not in any way attack the tissues of the plant on which it grows. 
In 1908 these statements were challenged by Maire (3) on observations 
which he had made on four fungi of the genus Meliola. The view held by 
some of the earlier workers that the Meliolas are entirely superficial and 
grow like the Capnodiums on the honey-dew produced by insects, he rejects 
on the grounds that close observation has shown that the development of 
these fungi is quite independent of the presence of any insects. 
A second hypothesis is that the fungus derives its nourishment by 
osmotic interchanges between their hyphae applied to the cuticle and the 
epidermal cells. Maire observes that this is improbable, since the hyphae 
are separated from the cavity of the epidermal cells by a layer of imper- 
meable cutin, of which the thickness is often several times that of the 
hypha. Moreover, the effect of the Meliolas on their host — neglected by 
most authors — is quite evident in certain cases ; for instance, extended 
purple spots are found on leaves of Schinus, radiating from the point covered 
by the Meliola mycelium, and no other cause can be found for the dis- 
coloration. 
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