17 
Drummond, in his striking and well-known book, ‘‘ The Natural 
Law in the Spritual World, ’’ might have given usa chapter on 
parasitism in its relations to the interesting subject now before us. 
Examine a lichen—a fertile one—and you will see some little 
plate-like bodies, sometimes with a thickish margin and sometimes 
without, sometimes of the same colour as the thallus and some- 
times of a different one. These are the apothecia—the so-called 
fructification—which contain the asci, along with certain threads 
called paraphyses. The asci may be likened to a row of tiny soda- 
water bottles turned upside down, and containing spores. These 
latter are splendid microscopic objects. Their number is constant 
in the same species, and is usually four or a multiple of four—very 
often eight. There may, however, be only one, and there may be 
over a hundred. In their form there is the greatest variety. ‘They 
are not commonly one-celled, as they are very apt to double their 
number by each one dividing into two, and, as the case may be, 
they are said to be 2,-4,-6,-8, or multi-septate. They require 
rather a high power—say 400 diameters—with your microscope, 
but they are amongst the most interesting of objects, and wonder- 
ful enough to be warmly commended to the notice of any Micros- 
copical Society. The idea that a syoreis always a tiny round simple 
cell is quite a mistaken one, for, in its numerous forms and variety 
of colours, it delights the student. On the surface of the lichen- 
thallus, generally at or near the margin, are little blackish spots 
called spermagones which contain spermatia, and are supposed to 
fertilize the spores of the apothecia. The Spermatia are exceedingly _ 
small, and not provided with any cilia, so that they do not resemble 
zoospores, Which can, for a time, move about freely. Dr. M. C. 
Cooke, in his ‘* Introduction to the Study of Microscopic Fungi,’ 
has a very good chapter on spermagones. Speaking of the dis- 
charge of the spermatia from the spermagone he says—‘‘ to com- 
pare minute things with gigantic, as a recent author has observed, 
it resembles the lava issuing from the crater of a volcano.’ Bear 
in mind that spermagones are not pecudiar to lichens and that they 
are commonly but not always found on the same thallus as the 
‘apothecia. Some lichens have neither apothecia nor spermagones, 
but are more or less covered with soredia—powdery heaps of 
gonidia they are—and by means of them the species are repro- 
duced. This is a genuine illustration of vegetative reproduction, for 
the old plant throws off part of itself to form its like as many 
plants, for instance one of the Garlics common on our cliff, throw 
off bulbils to continue their species. 
Any lengthy remarks on the classification of lichens would be 
out of place this evening. Nylander, De Bary, Tulasne, Acharius, 
Leighton, Orombie, Fries, (and others), have performed the difficult 
