206 DR LAUDER LINDSAY ON THE SPERMOGONES AND PYCNIDES 
narrow, linear, or sub-linear segments. These black points are the ostioles, which 
are usually round and very minute, but which are sometimes elongated, even 
lirelleeform, as in some forms of P. sinuosa. Sometimes the punctiform ostiole is 
perched on a pale thalline papilla or wart, as in some forms of P. tiliacea. As in 
most lichens, the ostiole, in the old state, is generally large and gaping, and it 
then frequently has a prominent ring-like border. The thallus is sometimes 
studded over with black, large, irregular perforations—frequently lacerate or 
stellate-fissured—as in P. stygia, P. trisiis, and P. saxatilis, var.omphalodes. The 
black punctiform spermogones frequently resemble parasitic Spherie, for which 
they were generally or often mistaken by earlier lichenologists. Seldom are they 
distinctly papilleeform, tuberculiform, or barrel-shaped, as in P. perforata var. 
denticulata. In the latter lichen, which is altogether an exceptional and anoma- 
lous one, the spermogones are very large barrels, studded on, and forming part 
of, the margins of the lobes, precisely as in the genus Platysma. What is* still 
more curious, they either occur alone, or they are associated on the same speci-' 
men with the ordinary black, punctate spermogones of P. perforata. Generally, 
the punctiform ostioles are extremely minute, as in P. sazatilis; they are of 
the same character, but rather larger and more distinct in P. perlata, P. physodes, 
P. tiliacea, P. perforata, and P. conspersa. From the fact that the ostiole, or 
that part of the apex of the spermogone which generally projects or is most 
visible on the surface of the thallus, is black usually, while the colour of the 
thallus itself is glaucous or gray, the spermogones of Parmelia are generally 
readily recognised. They are usually scattered, in considerable numbers, ‘out- 
side the region of the apothecia, on the surface of the thallus. In exceptional 
cases, they are confined to the margins of the laciniz or lobes, to which 
they give a more or less denticulate character. On the flattened linear lacinie 
of P. tristis they are small, and not very prominent; but in var. denticulata of 
P. perforata they are very large and conspicuous. Sometimes they are distri- 
buted on the flat surface of digitate expansions from the margins of the thallus, 
as in a form of P. perforata from the Organ Mountains, Brazil. Occasionally 
they are dotted over the exciple of the apothecia, and even on the saucer-like 
cavities left by the falling out of the disk in degenerate apothecia, as in P. con- 
spersa. In number the spermogones are generally considerable, even when 
merely dotted over the margins of the lobes. But sometimes they are dotted in 
great profusion over the whole surface of the thallus, as in P. encausta, P. 
olivacea, P. stygia, and P. conspersa. In the last-named species the name might 
be supposed to have been given in allusion to the great abundance of the spermo- 
gones. The walls or envelope of the spermogones are generally thick, and of a 
brown cellular tissue; they are frequently of the same structure as the epidermic 
or cortical layer of the thallus. The cavity is usually simple; the internal tissue 
dense, horny, hygrometric, and pale grayish. In the oldstate of the spermogone, 

