GEOGRAPHICAL DISTRIBUTION OF MOSSES. 75 



the great boulders which are scattered over the plains are 

 the habitats of Alpine mosses, such as Andreaa rupestris, 

 Catoscopium nigritum, Grimmea leucophylla, G. tricophylla, 

 which can scarcely be considered as the natural mosses of 

 such situations, but may probably be classed as remains, 

 being possibly survivors of species borne from their native 

 Alps upon these boulders during the glacial period." So 

 that it will be seen from the foregoing that there are many 

 anomalies in the geographical distribution of mosses, and 

 that at present our knowledge is too limited to admit of a 

 truly scientific exposition of the subject. 



In the Introduction to the " Synopsis," chap, v., Prof. 

 Schimper gives an interesting account of the geographical 

 distribution of mosses in Europe. He divides the whole 

 area of Europe into three zones. 



i st. A northern zone, extending from the Arctic circle 

 to the sixty-fourth parallel of latitude, embracing North 

 Russia and the Scandinavian peninsula, and at its western 

 end descending to 57, so as to take in the north of Scot- 

 land. 



2nd. A middle zone, embracing all the country between 

 the 6oth parallel of latitude, the German Ocean, and the 

 south foot of the Alps, or a line on the forty-sixth parallel 

 of latitude from the outlet of the Danube to the mouth of 

 the Garonne. 



3rd. A southern zone, extending south of the forty-sixth 

 parallel of latitude to the Mediterranean and Black Sea. 

 The northern zone presents sufficiently marked characters 

 in the vegetation to indicate two divisions, which he calls 

 the Arctic-northern and southern-northern zones. In the 

 Arctic zone about 200 species are found; in the lower zone 

 nearly 500 species, or about two-thirds of the whole Euro- 

 pean moss flora. But Whilst the species in the Arctic zone 

 are few in number, individually they are represented in such 

 numbers as to give a characteristic feature to the landscape. 

 The Polytricha, occurring in great masses, give quite a weird 

 look to these inhospitable regions : here and there occur 

 vast bogs covered with Sphagnums, and on the surround- 

 ing rocks black tufts of Andreaeas and Grimmias. But here 



