496 DR. LINDSAY ON NEW-ZEALAND LICHENS. 
whole spore-cavity, separated only by a narrow linear septum or interspace, are about 
half the usual size, or about the size of the terminal loculi where the spore is quadri- 
locular, are seated at the opposite poles or extremities of the spore, and are connected 
generally by a narrow linear tubule, which runs up the long axis of the spore*, The 
apothecia do not vary much in external characters. The disk is usually flat, and of various 
shades of red or brown, girt by a thickish distinct exciple of the colour of the thallus. 
Both disk and exciple, however, are subject to various forms of degeneration. The 
former may become urceolate from shrinkage, or biatorine and convex from turgescence, 
or it may become partly or wholly eroded, or it may fall away entirely, leaving only an 
irregular saucer-shaped scar, which is whitish or yellowish, generally according to the 
colour of the medullary tissue of the thallus; or it may become the site of the black 
parasitic Celidiwm Stictarum, Tul. (figs. 26, 27 ), which quite alters its appearance, render- 
ing it irregularly tuberculate as well as black. Misunderstanding the nature of this 
deformity, Fée arranged the species affected by this parasite in separate genera, Delisea 
and Plectocarpon | Nyl. Syn. 352]; while other authors have described them as varietiest. 
The exciple, or apothecial margin, sometimes becomes fringed with minute squamulose or 
granulose growths, similar to those which occur also on the thallus; or it is pilose or 
tomentose, like the thallus; or it rises above or sinks below the disk, or becomes thick- 
ened or attenuated, or it disappears. 
3. Thallus.—Its colour (cortical layer) is generally some shade of brown, yellow, 
or crimson, or some combination of these colours. Under water, many herbarium spe- 
cimens of a buff or brown tint become brilliantly green, or assume various duller shades 
of that colour on the upper surface of the thallus, the under surface being generally 
unchanged, or being only deepened in its usual brownish #int. Those with a yellow or 
red thallus also acquire various shades of green. Species with a greyish-brown thallus 
become deep slate-coloured (bluish black); and generally at the same time they exhale 
the peculiar strong odour so characteristic of our Stictina fuliginosa and S. sylvatica. It 
would appear, indeed, that the colour of the thallus bears a close relation to the degree 
of moisture and exposure to light. The medullary tissue in a large section of the Sticte is 
whitish, in another it is of various shades of gamboge-yellow. It is generally prominently 
exhibited, from the contrast of its colour to that of the cortical layer, wherever there are 
fissures or erosions of the latter, or cephalodia, cyphelle, pseudo-cyphelle, isidia, oF 
soredia, all of which are more or less abundant on the thallus of the Sticte. The colour, 
however, both of cortical and medullary layers varies occasionally even in the same 
species, so that, as a diagnostic character, colour per se cannot be altogether relied on. 
* Exceptionally (e. g. in Sticta serobiculata, Ach., from Inverary, Scotland) I have found the epispore coloured 
blue, like the thecæ, under iodine—a circumstance which also occurs in the spores of Parmelia megaleia, Nyl., and 
a few other lichens, 
t The Celidium affects also the thallus, either upper or under surface, generally the former, seated on and pro- 
bably producing cephalodiiform tubercles, that fr equently resemble those apothecia which are rendered difform and 
degenerate by the growth of the same common parasite [Nyl. Syn. 352]. It occurs also on cephalodia proper © r 
those of Ricasolia corrosa [Nyl. Syn. 372]. The parasite appears thus to affect alike species of the genera m 
ues. and Ricasolia (Linds. Observ. on new Lichens and Fungi from Otago, N. Z., p. 452, plate 33% = 
OSES? ae Sa Oe EINEN EIERN ET 
lp PEERS RR ae CT ae Se ae ee EU ROTE TE 
