114 DR LAUDER LINDSAY ON THE SPERMOGONES AND PYCNIDES 
d. Concolorous with the thallus in Usnea, Ramalina, Thamnolia, Stereo- 
caulon, E/phebe, and Lichina. 
IV. Size of the Spermogones.—Their diameter varies from {th to th of an inch, 
many having an average diameter of —th to + th. 
They appear as extremely minute, microscopic points in many Parmelias, in 
Evernia, and Roccella. They are visible to the naked eye, or are readily recog- 
nized under a simple lens of low power, in many Rcasolias and Cladonias, and in 
some Usneas, Ramalinas, Physcias, Coccocarpias, and Placodiums. They are of 
an intermediate size in Sticta and certain Physcias. 
V. Number of the Spermogones.—They are seldom single and isolated, but this 
sometimes occurs in the terminal spermogones of Cladonia. In some species with 
a fruticulose thallus, such as Cladonia rangiferina, or C. furcata, and Cetraria 
aculeata, they are generally in groups of two or three. The papilleeform, mam- 
milleform, and wart-like spermogones, are generally grouped in larger number; 
but they never occur in such numbers as the punctiform ones. The latter some- 
times cover the whole surface of the thallus, so as to give it a black-punctate 
character, as in Parmelia encausta, P. conspersa, and P. stygia. 
VI. Structure of the Spermogone.—Every spermogone consists of the following 
parts :— 
1. A capsule or envelope. 
2. A nucleus, which again is made up of— 
a. Sterigmata, which generate ; 
b. Spermatia; and of a 
c. Basal cellular tissue. 
3. A central cavity, which opens to the external surface by a more or 
less minute 
4. Ostiole or Pore. 
1. The capsule or envelope is usually more or less thick and tough in its texture. 
It is made up of cells, sometimes round, but more generally, from their close 
ageregation and mutual pressure, hexagonal or irregularly angular, oblong or 
elongated. They are usually more or less thick-walled. Sometimes so close is 
their apposition, that the outline of the individual cells becomes lost, or is very 
indistinct. The structure of the capsule may be described, in general terms, as 
closely resembling that of the exciple of the apothecium and the cortical layer of 
the thallus. Its colour is as described under that of the spermogone generally. 
It is very frequently blackish or brownish; indigo in Pannaria triptophylla; 
orange in several Physcias and Placodiwms. 
2. The nucleus is mainly made up of the closely aggregated sterigmata, which 
are united by a mucilage, that also occupies the spermogonal cavity. Its texture 
is dense and more or less horny, frequently to such an extent that it admits of 
being sectioned in very thin slices. The texture becomes denser and harder 
