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XX. On Mycoidea parasitica, a new Genus of Parasitic Alge, and the Part vu: 
plays in the Formation of certain Lichens. By Davip Dorota CUNNINGHAM 
M.B., FILS, Surgeon H.M. Indian Army. 
(Plates XLII. & XLIII.) 
Read June 21st, 1877. 
I. Introductory ; Descriptive Characters ; and .Life- History of Mycoidea. 
NOW that the recent researches of Cohn and others have directed attention to the 
. occurrence of Algal parasites, it may be of interest to record the occurrence in 
India of a form which not only appears to be the highest yet observed to play a truly 
parasitic part, but which possesses even greater points of interest in the nature of its 
characters as compared with Dia of its nearest allies, and in its relation to epiphyllous 
Lichens. 
At intervals during the past eight years I have met with specimens of the plant in 
various stages of development; but it was only during the course of the last six months 
that I have been enabled to work out the subject so as to obtain materials for a con- 
sistent narrative of its life-history. The first specimens were obtained on the leaves of 
a mango-tree in 1869. On these leaves an eruption of bright orange patches or 
pustules was observed. "These patches were at first sight regarded as of a fungal nature, 
but on close examination presented peculiarities of structure preventing them from 
being referred to any determined genus of Fungi. Subsequently other specimens were 
obtained on Rhododendron-leaves in the Nilgiris, on the leaves of species of ferns, 
Crotons, and various other plants in Caleutta, and on Tea-leaves in the Rumaun hills. 
'The discovery of their presence on the latter host plant attracted renewed attention to 
their nature; and when they were again encountered in abundance in Calcutta as a 
destructive blight on plants of Camellia japonica, an opportunity was afforded of care- 
fully studying their real nature and modes of development. As to the specific identity 
of the Algæ occurring on all these various hosts, I am as yet not in a position to form a 
definite opinion, as, unfortunately, beyond drawings of one form of fructification, I have 
not preserved the materials necessary for comparison in many instances. With regard 
to the specific identity of the plant, in many cases there can be no doubt; and I am 
strongly inclined to believe that this holds good for all specimens yet obtained, however 
various the nature of the host. If this really prove to be the case, it is, no doubt, 
remarkable, and in a sense lowers the parasitism of the Alga. One important feature 
common to most, if not to all, of the leaves affected was the existence of a firm coriaceous 
texture and a thickened epidermal covering. 
Leaving the discussion of any further general questions until a detailed description of 
the species observed on the Camellia has been given, I shall now proceed to describe the 
structure and life-history of the parasite, and the nature of the lesions which it produces in 
. SECOND SERIES.—BOTANY, VOL. I. ; 2U 
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