LICHENS. 3S 



nently in a gonidial state on their trunks, or instead of producing 

 apothecia, develope only those white pulverulent masses known 

 as soredia. Oaks, provided damp or want of sunlight do not 

 stand in the way, usually repay research ; and Ash-trees are almost 

 invariably clothed with Lichens. Wall-tops coated with mud 

 produce some terrestrial forms, including Feltigera, which spreads 

 in large patches, greenish when wet, grey when dry, and bearing 

 numerous chestnut-coloured apothecia on the edges. Collema 

 may be found there, too, a gelatinous genus with no cortical layer. 

 But Lichens which grow on earth are by no means numerous 

 with us. Turfy and sandy soils are what they chiefly affect, and 

 these are precisely what we do not possess. Bceomyces riifus^ 

 however — a terrestrial Lichen, having a bluish-white, pulverulent 

 thallus, and stalked, pinkish apothecia — occurs with one of the 

 scarlet-fruited Cup-Lichens {Cladonia digitata) on a certain piece 

 of ferny ground on the outskirts of Woodchester Park, which has 

 in other respects a very peculiar and distinct flora of its own. 

 Our hill-sides produce the Reindeer Lichen — well-known as form- 

 ing the principal food of that animal during Scandinavian winters 

 — and two or three allied species in some abundance. 



Amongst the localities easily attainable from Stroud, though 

 rather outside the radius I have been considering, Oakley Park, 

 Sapperton and Hailey Woods, and the stone wall separating the 

 Berkeley Canal from the Severn at Sharpness Point, deserve 

 special recommendation. 



The student of Lichens must remember that these plants are 

 not always easily seen, and careful scrutiny will often detect their 

 presence abundantly, where at first sight they seem to be wanting. 

 A pocket-lens for examining bark and stones will be found useful, 

 and rainy weather has at least this advantage — that it renders 

 them more conspicuous. They share with mosses this recommen- 

 dation — that after being collected they may be set aside without 

 anxiety, to be examined at any convenient opportunity. After 

 months, or even years, they can be restored to their pristine 

 condition by a few drops of water. 



As regards their examination, a general view of the thallus 

 can be taken with an ordinary magnifying-glass ; but for inves- 

 tigating the internal structure, the microscope is essential. Where 

 a section cannot be made, a small fragment of an apothecium 

 should be placed on a sHde in a drop of hydrate of potash, with 

 a covering-glass over it. When this fragment has become well 

 moistened, it must be rubbed down till it becomes transparent, 

 when a good quarter-inch objective will show the internal organs. 

 The colour, shape, size, and internal divisions (if any) of the 

 spores can then be observed, and the presence or absence of 

 paraphyses noted. In examining spores, accurate focussing is 



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