28 
objective under the stage, to be used as a condenser at any angle, as 
suggested by Dr. Mathews; the new slide with moveable cover for dry 
objects ; and a ‘“‘ Barlow lens,” to be used in the draw tube as an 
amplifier, 
FEBRUARY 9TH. 
ORDINARY MEETING.—MR. C. P. SMITH ON 
“ LICHENS.” 
Lichens were a tribe of plants generally aerial as to habitat, and de- 
rived originally from an intricate mycelium, which gave rise to a more 
or less perfect plant according to situation. They were allied to fungi on 
the one hand and algae on theother. The earliest condition of Lichens 
which we are able to perceive was a myceloid or filamentous mass of 
threads, which, when occurring on trees or fabricated wood, penetrated 
into the wood. Externally there was developed a number of globular 
bodies filled with chlorophyll, called gonidia, which were subsequently 
covered by the cortical layer of the thallus. 
Under the name Lichens were grouped together a vast mass of 
eryptogams, varying exceedingly in texture and form, but normally 
distinguished by a thallus. This thallus was in the most highly organized 
genera, composed of four layers or strata, named respectively the 
cortical, gonidiac, medullary, and hypothalline strata, The external 
form of the thallus was exceedingly varied, and in texture might be 
foliaceous, coriaceous, cartilaginous, membranaceous, or gelatinous. 
There were several species without any thallus ; these athalline species 
were generally parasites on other Lichens, 
The fructification of Lichens appeared to be of a three-fold 
character, consisting of apothecia, spermogonia, and pycnidia. In the 
former spores were contained, either embedded in gelatine or in little - 
sacs, called asci. These spores were discharged from the apothecia under 
the influence of moisture. The spermogonia and pycnidia also contained 
small bodies (spermatia), whose functions were probably reproductive. 
The uses of Lichens were several, and, in fact, scarcely any tribe of . 
cryptogams was of somuchimportance to mankind. Asdyestufis they had 
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a 
