88 The Scottish Naturalist. 



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Lecidea dehtitens, summit of Cairn Gowar, 187 1 ; and Pyrenopsis 

 phylUscella, Ben Ghlo, 1870. 



In concluding this notice of the Hchens, I may mention that 

 Pdtigera canina is used in Glen Tilt as a remedy for distemper 

 in dogs. It was probably on account of this real or supposed 

 medicinal property that Linne gave it its specific name. Some 

 other lichens are used in the glen as dyes. 



ALG^. 



All that I can say about these is that Mr Roy, during a few 

 days' exploration of the district, found upwards of eighty-four 

 species of Desmids, a list of which will be found at page 68 of 

 the fourth volume of this magazine, and which need not be re- 

 peated here. Though the district did not turn out so rich as Mr 

 Roy expected, still a more extensive search at a different season 

 of the year would probably add considerably to the list. It is 

 wonderful how many species may be found in a favourable 

 locality and season. I once collected over eighty species in less 

 than half an hour on the Sidlaw Hills, not far from Perth. 



FUNGI. 



In Glen Tilt there is much — very much — ground that no 

 mycologist would expect to be very productive, and which, in 

 fact, is not productive, of fungi. So many of these plants are 

 dependent on the conditions afforded by the shelter of woods, 

 so many grow on or near dead and decaying timber, that a wide 

 extent of grassy meadows — rich though such be in certain species 

 — and of heather-elad hills — the least productive of any ground — 

 cannot be expected to produce a great variety. Moreover, it is 

 not every kind of wood that provides the most favourable con- 

 ditions for the growth of fungi. Birch woods, for example, are 

 proverbially unproductive, while, on the contrary, woods of Scots 

 fir or of spruce — more especially if the trees stand so thickly as 

 to prevent or limit the growth of phanerogamous plants on the 

 ground beneath them — aftbrd a rich harvest to the mycophilous 

 botanist. And it is in such woods of natural growth that Glen 

 'I'ilt is deficient. Here is no such grand assemblage of native 

 firs as that of the Black Wood of Rannoeh, with its grand masses 

 of Hydiium imhricatiun — beautiful in its expanse of rich, brown 

 seal in ess — and H. I(Bvigatiini ; its Tranictcs pini and Polypoi'us 

 Schiveiniizii ; its groups of many species ol Boletus, including the 



