186 RARE TREES IX ABBOTSBURY CASTLE GARDENS. 



representatives in the northern. Going from east to west the zone 

 occupied by the northern forms readies from Japan to Northern 

 China, by Amour to Central Asia, Siberia, the Caspian, the north 

 of Persia, Caucasus, Europe, the Atlantic and Pacific sides of 

 North America, from Spitzbergen, Greenland, Alaska, to 

 the Azores, Canaries, North Africa, Arabia, and the Malay Archi- 

 pelago. Tropical forms, although not a majority, are met with in 

 this extensive area, but only in isolated stations, separated widely 

 from each other, leading to the supposition that they belong to an 

 anterior homogeneous vegetation. The latest geographo-botanists, 

 such as Engler and Drud, show this to be the case. The northern 

 forms, which occur at the present day in high latitudes and on the 

 tops of mountain-ranges, belonged, without doubt, to a flora which 

 occupied vast regions extending to the mountain ranges of Central 

 Germany, the glaciers of the Alps, the valleys of the Danube and 

 the Rhine, and the plains of Lombardy. The Alpine and northern 

 forms were thus able to spread and maintain themselves in many a 

 favourable station, and with the retreat of the glaciers the hardiest 

 plants re-occupied the homes they had abandoned, but some failed 

 to do so, among them SaUshuria adianfoides, of which we shall 

 have to speak farther on. During the middle of the Tertiary age 

 (Miocene) the flora of the world underwent further important 

 transformations, bringing in the new forms, which now grow only in 

 Asia, Africa, and America, but are extinct in Europe. It is from 

 plants of this period we are able to trace some of the immediate 

 ancestors of our living species. A large amount of fossil remains of 

 the Abietacese Conifers are found in the later Eocene beds. The 

 scales of the cones of Pinus have been found in Siberia and ia the 

 Himalaya, showing a previous connection with districts so widely 

 separated. The Oligocene beds of the South of France contain 

 Pinaster, Pinea, and Strohus. The flora of this period is remark- 

 able for its richness and variety of species, in contrast to North 

 America, which shows a great poverty especially of Monocotyledons. 

 The Palms had entirely disappeared from Europe. A Drac£Bna, allied 

 to D. Draco, which now grows in the Canaries and in Western 



