176 
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 Reessneria 
Aspidium Escheri 
Isoetes Braunii 
Taxodium dubium 
Glyptostrobus europzeus 
Sequoia Langsdorfii 
Sparganium valdense 
Liquidambar europzeum 
Populus mutabilis 
balsamoides 
latior 
Salix varians 
Ulmwus Braunii 
Planera ungeri 
Platanus aceroides 
Laurus princeps 
Hakea salicina 
Diospyros brachysepala 
W. radicans (a Madeira fern). 
A. thelypteris (a marsh fern). 
I. lacustris (common water-plant). 
T. distichum (American swamp-cypress). 
G. heterophyllus (Chinese cypress). 
S. sempervirens (redwood). 
S. ramosum (common water-plant). 
L. styracifluum (American shrub). 
P. euphratica (Asiatic poplar). 
P. balsamifera 
P. monilifera 
S. fragilis (common crack willow). 
U. ciliata (elm). 
P. Richardi (tree allied to the elms). 
P. occidentalis (plane-tree). 
L. canariensis (laurel of Canary Islands). 
H. saligna (Australian proteacean tree). 
D. lotus (kind of ebony-tree). 
American poplars. 
bi ddba dd dtd dtd ea 
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- 
ae required by the Theory of Descent. Let no one 
under-rate 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 paleontology. ‘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 piants 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. J 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 
