9 



probably the same species have survived to our own times . 

 He considers seventy-two plants as probably ancestral forms 

 actually identical with those now living. The following are 

 some of them : 



MIOCENE FORM. MODERN FORM. 



Woodwardia Rcessneria = W. radicans (a Madeira fern). 



Aspidium Escheri = A. thelypteris (a marsh fern). 



Isoetes Braimii = I. lacustris (common water-plant). 



Taxodium dubium = T. distichum (American swamp-cypress) 



Glyptostrobus europseus = G. heterophyllus (Chinese cypress). 



Sequoia Langsdorfii = S. sempervirens (redwood). 



Sparganium valdense = S. ramosum (common water-plant). 



Liquidambar europseum = L. styracifluum (American shrub). 



Populus mutabilis = P. euphratica (Asiatic poplar). 



- P. 



Salix varians = S. fragilis (common crack willow). 



Ulmus Braunii = U. ciliata (elm). 



Planera ungeri = P. Richardi (tree allied to the elms). 



Platanus aceroides = P. occidentalis (plane-tree). 



Lauras princeps = L. canariensis (laurel of Canary Islands). 



Hakea salicina = H. saligna (Australian proteacean tree). 



Diospyros brachysepala = D. lotus (kind of ebony-tree). 



Besides these his list includes also the direct ancestors of three 

 species of maples, of the tulip-tree, and so on. This extra- 

 ordinary permanence of generic, and possibly even of specific 

 type, is strongly opposed to any theory of variation. If 

 genera, and possibly species, have changed so little in so vast 

 a time there really is no room for the slow and secular trans- 

 formation required by the Theory of Descent. Let no one 

 underrate the value of this kind of evidence founded on leaves 

 and flowers. The microscope is now able to decide points of 

 affinity in plants to an extent never dreamed of in the earlier 

 days of palaeontology. The cells of the epidermis, with their 

 shape and arrangement, and the stomates which pierce it 

 with their characteristic forms, are often sufficiently preserved 

 in Miocene leaves to indicate the order, if not the genus, of 

 a mere fragment. 



But there is another point of view from which the persist- 

 ence of these genera is very striking. They have outlived a 

 most remarkable change in the climate of Spitzbergen and 

 Greenland. Genera of plants are still living in the warm 

 temperate zone which once flourished within the present 

 Arctic circle. This is well known as one of the greatest 

 puzzles in geology ; but I am not now concerned with its 

 solution. I am only pointing out that beeches, oaks, planes, 

 poplars, and so on, are older than that extraordinary con- 

 dition of our planet which allowed a vigorous growth of 



