188 RARE TREES IX ABBOTSBURY CASTLE GARDEN'S. 



G. adiantoides in the basalts of Ardtun Head, Isle of Mull. It 

 is found in Greenland, Italy, and in the Saghalien Islands, and 

 entirely disappeared from Europe in the Upper Miocene age. The 

 genus once so widely spread and indigenous in Europe, and Avhich 

 commenced its southward migration from the Polar regions as 

 long back as in the Eocene age, is now reduced to one species in 

 the far East, and owes its i^reservation to the agency of man. It 

 is capable of sustaining the ordinary temperature of Europe, as we 

 see here in. these gardens. It flowers and seeds in the Botanical 

 Gardens of Montpellier, and can live at Copenhagen, Lat. 55° 41' N., 

 where the mean temperature is about 46° Fah. It attains a height 

 from 60 to 70 feet. The small leaf-bearing twigs are thick, decidu- 

 ous, and tubercled, bearing a tuft of four or five closely-packed, 

 stalked leaves. The fruit is a one-seeded drupe with an outer fle?hy 

 covering. The Gingkos of' the Jurassic age bore persistent leaves. 



Taxodium. 



Flowers monoecious, branches slender, clothed with linear 

 deciduous leaves arranged in two rows, some of the branchlets fall 

 in the autumn. The Genus first appeared in the Arctic regions in 

 the later Cretaceous age, which were then interspersed with 

 large lakes fed by thermal calcareous, ferruginous springs. A 

 considerable number of conifers were introduced into Europe 

 during the Tertiary age in company with heecli, Liquidambar, 

 Tulip-tree, Lime, Elm, Sassafras, &c., which were subsequently 

 distributed over the temperate zone, and formed vast forests. 

 Europe was at that period broken up into islands. Taxodium has 

 not varied much from its j)rimordial type, and differs little from its 

 living representatives, Taxodium distichum and T. mucronatum, 

 both limited to IS". America, the former to the Southern States, the 

 latter to the mountainous districts of Mexico. 



T. distichum can scarcely be distinguished from the early Oligocene 

 and Miocene genus ; hence Professor Heer named it T. disticlmm. — 

 miocenicum — and is one of the most widely distributed of Tertiary 

 plants. 



