AND LIFE*HISTORY OF A TROPICAL EPIPHYLLOUS LICHEN. 109 
totally different Lichen is figured*. In systematically criticising those points in the 
paper referred to with which my observations do not agree, it should be borne in mind 
that I have had no opportunity of examining the Calcutta forms in their natural living 
conditions, and it is therefore not impossible that the Alga and Lichen described and 
examined by me may be specifically different from “ Mycoidea parasitica.” 
Cunningham figures (pl. xlii. fig. 8) a vertical section through the Camellia-leaf and 
its attached Alga, and figures certain green cells of the latter as passing through the 
epidermis of the leaf into the region of palisade cells. These descending cells apparently 
correspond to the “rhizoids” of my Pl. XIX. figs. 12, 17, & 18, and which I have never 
seen breaking through the leaf-tissuest. There appears to be some slight confusion 
between Cunningham's fig. 8 (pl. xlii.) and the sentence on page 304 of his paper :-- 
“ The filaments of the disk are seen to lie between the epidermis and the subepidermal 
layer of cells.” It appears probable that the condition of affairs here figured corresponds 
pretty closely with what І have observed іп Citrus (fig. 13), and that the Algal thallus 
had become developed between the cuticle of the Camellia-leaf and the more or less 
broken-down epidermis cells ; if not, the figure conveys the idea that the thallus is vege- 
tating on and not wader the epidermis, but that the cuticle of the leaf and that of the 
Alga have become coextensive. If the green prolongations are really protruded parasiti- 
cally into the leaf, two difficulties suggest themselves : why are they confined to a central 
tuft P and why do they remain green ? These difficulties are not explained by the context ; 
and it appears more than possible that the discoloration of the affected area of the leaf 
is due, not to direct parasitic action, but to influences similar to those exerted by the 
Algal thallus on the leaf of Michelia. Nothing in the figure suggests the definite forma- 
tion of a corky tissue; if this occurred, the brown colour and sloughing might be 
explained. 
My observations confirm generally, and extend in detail, the description of the filaments 
and “asexual fructification”’; but the observations on the so-called “ sexual fructification ” 
in the paper cited are in such startling contrast to my own, that serious doubts may be 
entertained either as to the identification of the two Cryptogams, or the aecuracy of 
Cunningham's description. 
Cunningham found that certain cells of the thallus (corresponding morphologically, 
apparently, with the zoospore-containing cells in my Pl. XX. figs. 39, 40, &c.) swell up, 
each forming “ап obovate dilatation," with a thick cell-wall, the orange-red protoplasm of 
which becomes accumulated into an “ oospheric mass," and the whole becomes an 
* оодотит.” 
The author goes on to say (р. 307): —“ Due to the dense nature of the disk (thallus), to 
its subepidermal site, and to the fact that, when detached from the leaf, only retrograde 
changes, tending to a recurrence to pure vegetative growth, occur in the developing fruc- 
* There is nothing remarkable in this: the same Alga often serves as host for several different Fungi; and I have 
evidence to the same end as Bornet, who refers the Lichens Verrucaria, Roccella, Chiodecton and several others to 
combinations of Chroolepus and a Fungus. Vide Ann. des Se. Nat. 5° вет. tome xix. p. 315 et seq. 
T Cunningham’s figure is by no means decisive: the appearance might easily be caused by “ dragging” of the 
rhizoids by the razor; and the beautiful bright-green colour of his “ haustoria” is not suggestive of parasitism. 
