SPENCER : THE AFFINITY OF DADOXYLON TO CORDAITES. 103 
There is one feature about Dadoxylon which has often struck me 
as being in singular contrast to what obtains in the higher cryptogams, 
such as the Sigillaria and Lepidodendra, and that is while in its 
woody structure it seems to be nearest allied to the Araucaria, which 
belongs to one of the lowest types of the Pine family ; on the other 
hand, the structure of its contemporaries, the Sigillaria and the 
Lepidodendra, shows us that they belonged to a far higher type of 
cryptogams than any living at the present day. The vascular 
cryptograms of the Carboniferous age had already reached their 
climax, both in growth and in organization, from which they have 
gradually dwindled down to their present lowly condition. 
But if Dadoxylon was a true pine no such degradation has taken 
place in the Pine family, which must have remained very much in 
the same state of development from its first known appearance in the 
middle of the Devonian period through the vast length of the Car- 
boniferous and Permian periods, and thence onwards through the 
great break at the end of the Carboniferous age into, and well nigh 
to the close of, the great Mesozoic ages. 
This, however, seems to many Palceophytologists utterly incredible, 
and is opposed by most of the other known facts in connection with 
the life of the same periods ; and of late years a considerable amount 
of doubt has arisen in the minds of some of our best fossil botanists 
concerning the affinities of our Dadoxylon. The weight of the evi- 
dence seems to me to be now in favour of the opinion that Dadoxylon 
and Cordaites belong to the same family, the cycads, and that they 
represent the highest type of that family, which, like the vascular 
cryptograms, have gradually dwindled away both in size and in 
organization until they have reached the insignificant forms of the 
present day. 
Those noble Cycadean trees, Dadoxylon and Cordaites, had 
already reached their climax in the Carboniferous age, and appear to 
have gradually died out towards the end of that period. 
Walchia imbricata, the first of the true pines, did not make its 
appearance until towards the end of the Carboniferous period. The 
first recorded specimen, according to Mr. R. Kidstone, F.G.S., was 
found a few years ago in the Upper Coal Measures. It is closely 
