AND LIFE-HISTORY OF A TROPICAL EPIPHYLLOUS LICHEN. 103 
following facts are easily ascertained, since the pycnidia are commonly produced in large 
numbers by the Lichen. 
The small black case, or hollow receptacle, arises directly from the brown hyphe of the 
investing mycelium, soon after the latter has commenced to invade the underparts of the 
Algal thallus (Pl. XVIII. fig. 4, Pl. XXI. figs. 60 & 62), and seems to be produced simply 
by the weaving of these hyph into a feltwork which gradually acquires a subglobular 
form (figs. 60-63), and the outer walls of which become dark-coloured and hardened 
as is common with such hyphe (fig. 64). Within this outer blackened shell is 
produced a more delicate lining of colourless filaments, closely matted together; from 
these are produced numerous short, slender база, directed in a convergent manner 
towards the centre of the hollow case; and from the ends of these dasidia are abstricted 
minute colourless basidiospores, or stylospores (figs. 64, 65), each of oblong shape, and 
with one median cross septum. When quite fresh, and examined in water, the very 
delicate septum is not easily recognized ; but four or five relatively large oily globules 
appear in the hyaline protoplasm composing the ground-substance of the spore. In 
aleohol or iodine, however, the globules disappear, and the septum becomes evident ; and 
an exospore can be distinguished (fig. 64) from the very delicate endospore, in many 
cases becoming wrinkled and contracted away from it like a pellicle. 
As the above-described stylospores increase in number and fill up the enlarging cavity 
of Ше pyenidium, a small, beautifully rounded aperture appears in the apex of the latter, 
through which the stylospores become extruded in masses, after the absorption of water 
(fig. 60), and are eventually scattered on the surface of the thallus and leaf. 
The tissues between the numerous pycnidia (figs. 62 ӛсе.) now consist of densely felted 
colourless and brown hyphee (fig. 65), in the interstices of which much air becomes 
entangled, and, in some cases at least, minute crystalline masses which effervesce on 
addition of acetic acid. Under these circumstances it becomes no easy matter to examine 
this dense feltwork, unless very thin sections be treated with acids and alcohol, stained, 
and mounted in glycerine. If picro-carmine be used the prepared colourless feltwork 
becomes dyed pink, the cuticle of the Lichen and leaf yellow. Close beneath the cuticle 
of the Lichen are to be recognized the ceils of the Alga, still containing more or less 
orange-red or green colouring-matter; and in some cases the rhizoid-cells with green 
contents may be observed among the meshes of the densely interwoven hyphe (figs. 69 & 
70). In no case, however, could I find either hyphe or “ gonidial cells ” "(ав the rhizoids 
«с. may be considered) penetrating into the leaf. 
After the colourless air-containing feltwork has become coextensive with the Algal 
thallus, filling up all the spaces between the cells, pycnidia, &c., and shining through the 
cuticle and more or less exhausted gonidial layers of the Lichen with an opaque white 
lustre, imparting the peculiar porcellaneous appearance so characteristic of the mature 
thallus (Pl. XVIII. fig. 3), the complete fruit-bodies or perithecia are pronus, always in 
smaller numbers than the pycnidia. 
Each perithecium (fig. 66) consists, as before, of an outer shell of coarser hyphæ, lined 
with a hymenium of densely matted, colourless, very delicate filaments, from which spring 
the asci and paraphyses in closely packed series, converging towards the upper part of the 
SECOND SERIES.—BOTANY, VOL, II. 8 
