MOSSES. 59 



The Rock Andraea we have from Blair Athole. It is a 

 commoner species, growing in short loose tufts, the stems 

 a .little branched, and its leaves blunt (A. rupestris, Plate 

 V., Jig. 13.) 



The Black Andraea (A. rothii) is still darker in hue, and 

 a little taller ; the leaves are awl-shaped. 



The Tall Andraea (A. nivalis) is of slender growth, and 

 is only found on the margin of perpetual snow. 



We went to the moors above Summer Lodge Bank in 

 search of the second group of the order, Bog Mosses 

 (Sphagnaceae.) We reached the neighbourhood of the 

 gloomy tarn, and began our search 

 among verdant patches of swampy 

 ground, while all around and 

 amongst the ling the soil was 

 covered with a thick carpet of 

 white moss, varied with a pink 

 hue. We soon collected several L andrjsa. 2. sphagnum. 

 specimens of Bog Mosses (Sphagnum.) These Mosses are 

 characterized by having their branches arranged in clus- 

 ters, their roundish urns on very short footstalks, and by 

 having no proper roots. As this group seems to be de- 

 signed by Providence to fill up water pools in bogs, roots 

 are unnecessary. The densely crowded stems have little 

 threads attached to them, by which they imbibe moisture : 

 as the plant grows, the under part decays and deposits 

 the used-up portions, while the acids, set free by the de- 

 composition of its parts, uniting with that given out by 

 other bog plants similarly decaying, forms a kind of 

 tannin, which preserves the substances imbued with it, 

 and renders them impervious to decomposition. This 



