182 
LINDSAY, ON LECIDEA LUGUBRIS. 
slightly roughened on its surface ; but I have not been able 
to detect any of the scobiform dust^ which occurs on the 
surface of the thalamium in Sphserophoron^ and which is due 
chiefly to the accumulation of the ripe spores^ along with the 
debris of the elements of the hymenium. 
The hypotheciiim consists of small_, roundish_, or irregular 
cellules^ of a brownish tint. From the hypothecium the 
thec(B arise as small oval vesicles^ which gradually become,, 
by elongation^ linear- cylindrical cells^ having a nearly uniform 
width throughout^ except below^, where they taper suddenly 
into narrow^ kneed or irregularly bent and longish pedicles. 
The thecal cell is at first full of a pale yellowish^ finely 
granular or grumous protoplasm. As the theca increases in 
size^ larger granules and globules make their appearance : 
these become agglomerated into globular masses^ which 
gradually assume the form of the future spores. Lastly, the 
cell-wall of the spore becomes visible, and is separated by a 
hyaline, distinct margin from the globular nucleus, which is 
of a pale yellow colour. For a considerable period the spores 
are glued together in a linear series, somewhat after the 
manner of the spores of Sphserophoron and some Calicia. 
Here, however^ the spores appear to attain to perfect 
maturity before they escape from the theca. Here, also, the 
spore-sac may generally be seen with tolerable distinctness, 
closely lining the interior of the thecal cell, at almost every 
stage of the development of the theca. Nor is the thecal 
wall ever so delicate in Lecidea luguhris as to be invisible, as 
in certain Calicia (e. g., C. tympanellum, Ach., Tulasne, Mem., 
pi. XV, fig. 18). Mature thecae generally measure from to 
inch, — the average being ^ Jo — length, by about ^ oVt7 
breadth. They generally come ofi" from the hypothecium in 
groups or bundles, six or eight thecse being closely aggregated, 
and the several groups of thecse are separated by similar 
bundles of paraphyses. They usually equal in length the 
paraphyses, and frequently project beyond them. When full 
of mature spores, the theca is a very beautifal object under 
the microscope : it may be likened to a narrow, colourless 
glass tube, containing a string of yellowish beads, of nearly 
the same diameter as the tube. The theca, when mature, 
becomes ruptured at the apex, giving escape to the spores 
one by one : these do not accumulate on the surface of the 
thalamium as in Sphserophoron. Under the reaction of 
iodine, the theca assumes a pale blue colour ; but this tint is 
not much better marked at the apex than below. This 
colour, struck by iodine, is indeed much darker and more 
distinct among the groups of paraphyses, which separate the 
