210 THE MEDALS OF CREATION. Cuap. VI. 
In conclusion, I must direct attention to a remarkable — 
character of the paleeozoic and secondary floras, namely, the — 
almost entire absence of the Graminec or Grasses, which con- — 
stitute so large a proportion of the existing vegetation. 
Above six hundred species of plants have been discovered — 
in the British strata ;* and yet two species of Poa (a tribe — 
of grasses), from Coalbrook Dale, are the only known exam- — 
ples of Graminez. It has been suggested that the greater — 
or lesser durability of the foliage oP certain vegetables, may — 
have occasioned their presence or absence in the carbonifer- — 
ous deposits, and experiments were instituted by Dr. Lindley 
with the view of determining this question. But though — 
it was found that, when the foliage of various families was — 
subjected to long maceration, the leaves of dicotyledons and — 
grasses disappeared, while those of ferns and cycads re- — 
mained, this fact does not meet the exigencies of the case, — 
for we have no evidence to show that the fossil leaves were — 
ever placed in similar conditions; on the contrary, there is — 
reason to conclude that they were imbedded under cireum- — 
stances that arrested the usual progress of decomposition, 
prevented the escape of the hydrogen and other gaseous — 
elements, and gave rise to the bituminous fermentation by — 
which they were converted into lignite and coal; and we © 
have no proof that, had grasses been associated with the — 
ferns, they would not have undergone a similar change. © 
Moreover, there are countries in which the ferns now assume 4 
the numerical proportion of the grasses of other latitudes; — 
a example, New Zealand, which also prea in its fauna a 
almost i entire absence of indigenous mammalia ; one species % 
of Rat being the only eognal living quads 2 
On this subject Dr. Dieffenbach roniabiel that “although — 
in its flora New Zealand has some relationship with the — 
