VOL. I. | Recent Literature. 77 
anterior to the Mesozoic. The remains. occurring in older forma- 
tions, and usually attributed to this class, are either too imperfect to 
permit of certain classification, or may better be referred to other 
groups. Of living genera Araucaria is certainly known as far back 
as the Jurassic, and Sequoia as the Cretaceous; Ginkgo is still older. 
A special chapter is devoted to the Cycads and Medullosz, and 
another to the remarkable entirely extinct group of the Cordaitez. 
To the latter, which are separated entirely from the Coniferz, are 
referred many of the remains of fossil wood which have usually been 
supposed to belong to the Conifer. The most interesting point in 
‘connection with them is the discovery of flowers, both male and fe- 
male, in a sufficiently perfect state of preservation to give a very tair 
idea of their structure, which differed materially from that of any 
living gymnosperms. The pollen grains are preserved with re- 
-markable perfectness, even showing a group of cells within which is 
assumed to bea sort of rudimentary prothallium like that in the 
pollen of other gymnosperms, but much more highly developed. 
These points seem to warrant the separation of the Cordaitez as a 
class, co-ordinate with the Cycads and Conifers. 
The chapter on the ferns is especially interesting and suggestive. 
While a considerable number: of ferns have been found with well 
preserved fructification, all of these in the formations below the Me- 
sozoic, that can be positively determined, show affinities with the 
Marattiaceze and, perhaps, with the Ophioglossez. This fact is es- 
pecially significant, as it entirely reverses the ordinarily accepted 
arrangement of the leptosporangiate and eusporangiate ferns. The 
former—z. ¢., those ferns in which the sporangia are of strictly epi- 
dermal origin—are usually regarded as the simpler forms from which 
the Eusporangiatz, or those forms with massive sporangia, like the 
Marattiaceze and Ophioglossez, have been derived. . 
As the Leptosporangiate have firm sporangia that ought to have 
been preserved in a fossil state, it is difficult to account for their ab- 
sence from the coal measures and earlier formations, if they really 
existed when these were forming. It seems probable that they are 
really later, more specialized forms, derived secondarily from the 
more primitive Eusporangiate. This view accords, too, with the 
evidences of embryology, and simplifies very much the problem ot 
the origin of the phanerogams. The remains of hydropterides are 
very scanty, and only a few remains from the tertiary are beyond 
dispute. 
