228 ON APHYLLOSTACHYS. 
Alyce, but, as terrestrial plants, their appearance could not be looked 
for until the terrestrial flora was ushered in. And that is the case, 
for we meet with them on Ferns of the Coal period. The other cel- 
lular plants are entirely wanting in Palaeozoic strata; they make their 
appearance only in the Tertiary period, and perhaps have not existed 
earlier. 
In a strict succession according to the theory of progressive deve- 
lopment, there is here a serious break- down ; nevertheless we may 
assert that vegetation on our globe commenced with the lowest form 
of cellular plants. 
The higher Cryptogams, as the Selaqbtem and Calamaria, now ap- 
pear in a state of development and perfection that is not reached in any 
subsequent period ; but at the same time there also are associated with 
them such herbaceous forms as we have at the present day. There is 
no transmutation from one species to the other in this large Order. 
The existence of Monocotyledons in the Palaeozoic period cannot be 
doubted, in my opinion, judging from a flower-bud resembling that of 
some recent Scitaminea. If it really did belong to Noggerathia, as is 
most probable, then the Monocotyledons have furnished their full 
share towards the formation of coal. The curiously-formed Catamites 
and Sigillarice, without any preparatory type, and not developing 
into any higher,— for they stand and fall with the younger divi- 
sion of the Palaeozoic period, — occur together with Gymnospenns 
{Conifers and Cycadea), which display a greater perfection than m 
any subsequent period. All the lower stages of the vegetable king- 
dom, — cellular plants, higher Cryptogams, Monocotyledons, and even 
Gymnospenns, — already existed in the Palaeozoic period; but the ap- 
pearance of genuine Dicotyledons has still to be discovered. Ihe 
Trias, which succeeds, has, in the Bunter Sandstein, a number ol 
forms not represented in the present flora, but they belong to already 
existing families, and there is a gradual replacing of extinct Orders 
and families by a superabundance of Ferns and Cycadea. The same 
remark applies to the whole Jura formation, with the exception of the 
single genus which I shall presently describe. In the Cretaceous pe- 
riod, however, genuine leaf-Dicotyledons appear, and there is w° m 
that time a constantly increasing approximation towards the flora o 
the present time; and this proceeds until, in the Tertiary period, the 
balance is turned, and the living forms predominate. 
