OF FILAMENTOUS, FRUTICULOSE, AND FOLIACEOUS LICHENS, 113 
Others, in addition to terminal spermogones, have barrel-shaped ones, of similar 
size and form, seated either on the horizontal primary thallus, or on the folioles 
or squamules which cover the podetia, as in C. alcicornis, C. squamosa, var. ccespi- 
titia, and C. bellidijiora ; or, in the same cases, they occur on the horizontal thallus 
or the folioles alone. 
In some species of Alectoria and Neuropogon, the spermogones are the terminal 
bulgings of the ultimate ramules, as in A. Taylori and N. melaxanthus. 
In Stereocaulon, they are warts usually crowded in groups at or about the ends 
of the ramules. In some species, they form a sort of collar round the terminal 
apothecia. 
In Spherophoron, Acroscyphus and Lichina, they are seated on or near the tips 
of the ultimate divisions of the thallus. . 
In addition to the above normal or usual positions of spermogones, they some- 
times occur in the following exceptional situations :— 
a. On the exciple of the apothecia, as in P. conspersa. 
b. On the apothecia themselves, as in Lichina pygmea and conjinis, and 
some forms of Cladonia rangiferina. 
¢. In the hypothecial tissue of the apothecium, as in Celidium jfusco-purpu- 
reum. (Tul. Mem. Pl. 14, f. 12.) 
Ill. External colour of the spermogones.—Iin immersed or semi-immersed sper- 
mogones, it is generally only the superior portion, or that portion which projects 
above the surface of the cortical layer of the thallus, that is coloured. In many 
cases the ostiole alone, or its margin, is the seat of visible colour. The naked or 
sessile spermogones, however, are usually coloured uniformly all round, the ostiole 
here, as in all cases, being darker than the surrounding tissues. 
The spermogones are generally differently coloured from the thallus, the one 
being dark and the other light ; and this contrast of colour is one reason why the 
spermogones are frequently so readily visible under the lens. In cases where 
both thallus and spermogones have a dark or a light colour, the latter are generally 
with difficulty recognised, as in Umbilicaria, Usnea, and Ramalina. The colour 
of the spermogone generally passes more or less gradually into that of the sur- 
rounding thalline surface. But sometimes the spermogone is distinctly circum- 
scribed, both as to colour and form, as in Collema and Leptogium, where its 
brownish-yellow colour contrasts well with the green of the thallus. 
The spermogones are :— 
a. Black in many Parmelias, Physcias, and Roccellas. Some of them, 
though black to the naked eye, or under the lens, or when dry, are 
found to be really b70wn when submitted to the microscope, or when 
moistened. 
b. Brown in Cladonia, Nephromium, and some Physcias and Parmelias. 
c. Orange-red or yellow in several Physcias and Placodiums. 
VOL. XXII. PART I. 2G 
