PYCNIDES OF CRUSTACEOUS LICHENS. 235 
the spermatia are longish, subfiliform, and curved or twisted, as in Lecanora subfusca ; 
while in the other they are subspherical, and atomic in size. Neither of these forms of 
spermogone may be considered really referable to the Pertusaria. Nylander (Scand. 
p. 177) describes the spermatia of the genus as acicular. 
Tribe II. LECIDEEI. 
Genus I. LECIDEA. 
This large and heterogeneous genus is by far the most important among the Lichens, 
whether as respects :— 
- (a) The variety in the form of its Spermogones and their contents ; 
(b) The possession of Pycnides in addition to Spermogones ; 
(c) The possession of several forms of Spermogone or Pycnide, or both ; 
(d) The similarity, externally, of its Spermogones and Pyenides, in at least many cases, 
to parasitie or associated 
l. Microfungi, 
2. Microlichens, 
3. Fungo-Lichens. 
The character of the spermogones, especially, is so varied that they demand a more sys- 
tematie description than those of other genera, whether of the higher or lower lichens. 
I. Spermogones :— 
(a) Site. They are sometimes scattered equally or generally over the thallus and among 
the apothecia. More usually they are confined to the peripheral parts of the thallus, 
outside the region occupied by the apothecia. In species with a squamulose or areolate 
thallus, they are frequently seated in one corner of the squamule or areola, either singly 
or in groups of two or three. In contigua and fusco-atra they occur singly on corners; 
in lurida, decipiens, and glauco-lepidea two or three are seated on each, generally sterile, 
- squamule. In sanguinaria they are perched on warts or granulations of the thallus; in 
geographica they are dotted over the areolæ. In subfoliaceous species (such as canescens), 
they resemble in site and other external characters those of Parmelia or Physcia*, occur- 
ring in canescens as black cones on the laciniæ. Exceptionally they are seated appa- 
rently directly on the bark or rock on which the apothecia or the thallus grow; that is 
to say, they are analogous to athalline apothecia in possessing no thallus. In such cases 
it is frequently, if not always, difficult to determine whether they belong to the associated 
thallus or apothecia, or to some species of Lichen or Fungus, whose other forms of fruit 
are not exhibited in a given specimen. 
(b) Form. By far the commonest forms are those which are represented on the surface 
of the thallus by a minute, frequently microscopic, point or papilla, the body being in the 
first case wholly, and in the second partly, immersed. Many of these can only be seen 
(and sometimes even then with difficulty) under moisture, with the aid of the lens. But 
others are quite visible to the naked eye, and are among the largest, most conspicuous 
* As figured in my first Mem. Spermog. plates xi., xii., and xiii. 
