1890-91.] 297 



The fifth meeting of the Winter Session was held on Tuesday 

 evening, February 17th, the President in the chair, when two 

 papers were read. The first was by Mr. Henry Davis, his 

 subject being " A Chat about Lichens." The reader stated 

 that he was led to take up the study of lichens some time 

 ago, on account of the interesting objects that parts of these 

 plants offer for the microscope. He did not think that this 

 subject had been brought before the Club by any of its 

 members, and he wished to draw their attention to these inter- 

 esting plants. They give patches of colour to quaint bits of the 

 landscape, and are on that account dear to artists and lovers of 

 the beautiful in nature. They abound almost everywhere, 

 growing in shrubby tufts, in long beard-like filaments, in 

 powdery patches, and dark stains, and on all sorts of materials 

 — on trees, rocks, moss, earth, and even on other lichens. 

 Lichens take their sustenance from the atmosphere, and merely 

 attach themselves to the materials on which they are found. 

 The Rev. W. A. Leighton, a celebrated lichenologist, says that 

 " these plants grow in perfection only in pure air, and their 

 abundance in a fully-developed and fruiting state is a sure and 

 certain indication of the purity of the atmosphere and salubrity 

 of the climate." The older botanists held that lichens were a 

 distinct order of flowerless plants, but some of the later 

 authorities believe that they are only unicellular Algce, on 

 which a fungus grows in a parasitic state. Mr. Davis pointed 

 out by the aid of a diagram how the thallus of a lichen is built 

 up, it being composed of three layers, namely — the first or 

 cortical layer, consisting of closely packed cells which form the 

 outer bark, as it were, of the thallus ; the second, or gonidal, 

 in which the green cells lie prisoners ; and the third, or 

 medullary layer, with its hyphos intertwined in a felty mass. He 

 also showed where the spores lay perdu in their theca, and 

 stated that if a thin section of an apothecium be made, or if a 

 bit be rubbed down in a drop of water, the spores make beautiful 

 objects for the microscope. Lichens are classed by the general 

 appearance of their thalli, by the colour, shape, &c, of their 



