312 DR. D. D. CUNNINGHAM ON MYCOIDEA PARASITICA, 
into zoospores, and the subsequent development of each of these into a compound 
cellular body—the so-called primary disk. | 
In certain respects it appears to be more closely allied to the genus Phycopeltis than 
to any other. The development of the zoospore into the primary disk is of the same 
nature as that by which the disks of Phycopeltis are formed ; there is the same absence 
of setz, the same colouring of the cell-contents, and the habitat (on the leaves of living 
plants) is similar. It is, however, distinctly marked off from that genus by the deve- 
lopment of the secondary subepidermal disk, and by the peculiar arrangement of the cells 
which produce the asexual fructification. 
In spite of the peculiarities which it presents, the close relation of this Alga to Coleo- 
chete and the allied genera is unmistakable; and all the departures from the ordinary 
type which it presents are explicable as the result of modifications adapting it to its 
parasitic habit and peculiar locality. The production of zoospores by the common cells 
of the disk would be useless, where such zoospores would be imprisoned beneath the 
epidermis of the host, and unable to find a fit site for their further development. So in 
regard to the sexual fructification; a process of fertilization by motile antherozoids is 
replaced by one effected by means of pollinodia, where the sexual organs, in place of lying 
free in a fluid, are buried in the tissues of a host plant. 
MYCOIDEA, nov. gen. 
Thallus entophyticus, disciformis, e filis articulatis formatus et filis erectis, aeriis, sporiferis przeditus. 
Cytioplasma aureum aut viride. 
Propagatio zoogonidiis et oosporis fit. 
Zoogonidia in cellulis matricalibus, que extremis filorum aeriorum superimposite sunt, formata. 
MYCOIDEA PARASITICA, Cunningham. 
Generis que differentia ezedem speciei. 
Zoogonidiis numerosis, diametro 0°00825 x 0:0052 m. m. 
Oosporis globosis. 
Habitat, Indize Orientalis, in fruticum et arborum foliis. 
Il. Its relations when attacked by Parasitic Lichens and Fungi. 
The first part of this paper has been occupied with the description of the characters 
and life-history of this Alga per se; it now remains to give some account of ‘its relations 
as a gonidia-former when in its turn subjected to the attack of parasites in the guise of 
fungal filaments. As far as my observations have yet gone, it may enter into the 
formation of various species of lichens, according to the stage of development in which 
it is attacked; but at present attention will be confined to one species, the development 
of which has been comparatively fully worked out, and which occurs on the leaves of 
Camellia japonica, of Nephelium, and of various other plants, all of which are — to 
the attacks of the Alga. 
It has been already mentioned that only a relatively small number of the primary 
disks give origin to subepidermal filaments, and that many of them dry up and disappear 
