A NEW GENUS OF PARASITIC ALGE. | 815 
surrounded by an abundance of slender somewhat capitate paraphyses (Pl. XLIII. 
fig. 21). I am uncertain whether any of the spores yet obtained were mature; but those 
showing most indications of being so were colourless or very pale yellow, somewhat con- 
stricted at the septum, and measuring 0:0227 x 0:0075. Numerous experiments 
were made as to the reaction of the asci with solution of iodine. In no instance was 
there any distinct indication of blue staining as encountered in most lichens observed. 
The walls of the asci, on the contrary, appeared to be unaffected į but the presence of a 
large quantity of the material styled epiplasma by De Bary was demonstrated around 
the spores, which, under such circumstances, appeared as pale yellow bodies embedded 
in a deep-red-brown basis. i 
The history of the development of this species of epiphyllous lichen appears in itself 
to afford a complete demonstration of the composite nature of such structures. There 
can be no doubt here as to the source of the gonidial cell, and that that source is an Alga 
capable of independent existence and of producing perfect forms of fructification. On 
the other hand, it is only in association with these algal elements that the fungal fila- 
ments form a tissue capable of giving origin to spermogonia and apothecia. 
Various other points might be touched upon ; but in the mean time I would merely 
suggest that the anomalous subepidermal site and so-called cephaluroid conditions of the 
various species of Strigula are probably explicable as owing to their gonidial elements 
belonging to Algæ identical with or similar to the species here described. The sub- 
epidermal site is at once explicable by the supposition of the entrance of hyphæ along 
with the filaments of the Alga going to the. formation of the secondary disks; whilst 
the cephaluroid condition may, so far as can be judged from figures at all events, be 
referred to cases in which the algal element has partially retained or regained the 
ascendancy, and has given origin to a crop of the asexual fructification normally 
belonging to it. 
In conclusion, it may be well to call attention to the fact that the existence of 
structures closely resembling the primary disks of the Alga forming the subject of the 
present paper has been already indicated by various authors. The organisms described by 
Mettenius as occurring on the leaves of ferns, and referred by Millardet to the genus 
Phycopeltis *, may with as much propriety be ascribed to the present genus. Even 
the relation of the disks to fungal elements would seem to have been noticed. For 
example, the Rev. Mr. Berkeley, in a paper on “ The Thread Blight of Tea,” mentions 
the occurrence on tea-leaves of ** minute shield-like bodies, consisting of cells radiating 
from a central aperture containing spores," and gives a figure which might well pass 
for that of one of the primary disks f. Mr. Archer also, in exhibiting some of Dr. 
Bornet's preparations, commented on one showing a minute lichen with its hyphe 
investing a form of Phyllactidiwm or Coleochete, and pointed out the singular habitat 
of the Alga, ** on the leaves of living trees in the tropics” 1. 
* o De la Germination des Zygospores dans les genres Closterium et Staurastrum et sur un genre nouveau d'algues 
Chlorosporées,” par M. A. Millardet, Mémoires de la Société des Sciences Naturelles de Strasbourg, 1870. 
T Quarterly Journal of Microscopical Science, 1875, p. 132. t Ibid. p. 334. 
