116 DR LAUDER LINDSAY ON THE SPERMOGONES AND PYCNIDES 
b. Compound or articulated | arthrosterigmata|. Component cells are,— 
1. Short, broadish, often thick-walled, and numerous in Sticta, Ricasolia, 
Nephromium, Pannaria, Coccocarpia, Placodium, Umbilicaria, Collema, Leptogium, 
and some Physcias. 
2. Longish, narrow, mostly thin-walled, and few in Bx mela, many Physcias, 
Evernia, Usnea, Platysma, and Cetraria. 
Like the simple sterigmata, the articulated sterigmata are sometimes ramose, 
but the ramifications may come off at any point between their base and apex. It 
is noteworthy, that arthrosterigmata uniformly bear stv,aight spermatia, which are 
given off from both apex and sides, while the simple sterigmata bear spermatia, 
which are sometimes curved or twisted, sometimes straight. In the case of simple 
sterigmata, the spermatia are more frequently short, oblong, oblong-oval, or cres- 
centic; in that of arthrosterigmata, they are almost always rod-shaped or acicular. 
In the arthrosterigmata, the spermatia, though given off from the sides of the 
sterigmatic filament, as a whole, are generated from the apices of the individual 
or component cellules, at more or less irregular angles. Hence they project from 
the sides of the sterigmata like a series of needles or bristles, numerous in propor- 
tion to the number of the constituent cellules of each sterigma. This bristled 
appearance is, therefore, most marked where the individual articulations or cells 
are short and numerous, as in Collema, Umbilicaria, and Placodium. 
(2.) Size.—In length, sterigmata vary from +th to = th of an inch, a medium 
being sei to th. They are shortest when simple ; in some cases so short as to 
eben absent. In breadth, they vary from ;.th to ;,1,th; an average being ,,th 
to 1 th. Simple sterigmata are usually narrower, as well as shorter, than arthro- 
10, a 
sterigmata; in them the breadth is sometimes so small as ;,,,th to ;,,th. Arthro- 
sterigmata are frequently’ ~ th to ~,th broad, though sometimes they do not 
exceed ;,t,th. The following micrometrical scale, applied to the dength of the 
sterigmata, may assist the reader :— 
to sq inch. 
Fry 
KS 
o 
B 
te} 
a, 
ol 
| 
. Very short, 
1 0 
2. Short, iis ee 
3. Shortish, mee _— 
4, Medium size, Be a ss 
5. Longish, : ; : : f sto stv 
6. Very long, nae ae 
The cavity of the spermogone, in many lichens,—as in Parmelia physodes, P. 
saxatilis, P. tiliacea, P. acetabulum, P. perlata, P. perforata, P. sinuosa, P. mutabilis 
P. conspersa, P. kamtschadalis, and in Ramalina, Usnea, and Evernia, almost all 
having compound or articulated sterigmata,—is occupied more or less by a lax 
network of very delicate anastomosing filaments. These would appear to be 
hypertrophied, sterile sterigmata; at least, the elongated ramose sterigmata of 
Cladonia seem to me to furnish a key to their true nature. They spring from 
