LINNEAN SOCIETY OF LONDOX. 69 



same time, towards the end of the Palseozoic period — the Angio- 

 ■sperins much later, high up in the Mesozoic. 



The origin of the Cycadophyta (an enormously numerous, varied 

 and advanced class in Mesozoic times) is generally admitted — they 

 came from the Pteridosperms, or Cycatlotilices, to use the older 

 name, to whicli Potonio and some others still adhere. Even 

 Pi-of. Chodat *, who is inclined to break up the Pteridosperms, 

 would admit that some of the plants grouped under that name 

 were on the line of descent of the Cycadophytes. Hence that 

 great and dominant class of Mesozoic plants appears to have been 

 derived from a highly organized preceding group, and in fact from 

 one of the two highest classes of Palaeozoic plants — a conclusion 

 wholly favourable to Dr. Gaskell's view. 



The question as to the Conifers is far less simple. There are 

 three theories in the field : — 



1. All Conifers may have come from Lycopods. 



2. All may liave come from Cordai tales. 



3. Part may have come from Lycopods and part from 



Cordaitales. 



I am not going to enter into the controversy now, but we will 

 see how tlie different views affect the question before us. 



If the Conifers as a whole were derived from the Palaeozoic 

 Lycopods, tliey came from a very highly developed earlier group, 

 though not from the highest. The Lycopod advocates now base 

 their case to a great extent on Lepidocarpon — a Lycopod which 

 had attained to the seed-bearing habit, or something very like it. 

 Fiu-ther, the Lycopods, if not morphologically among the highest 

 Palaeozoic plants, were probably the dominant class of that age, 

 at least in the coal-forests. 80 that on this view the Conifers 

 had, at any rate, a very distinguished ancestry. 



If, on tiie other hand, they sprang from the same stock with the 

 Cordaitales, then they may perhaps claim as their ancestors the 

 very highest of PalaBozoic plants. It is not likely, however, that 

 the typical Cordaitete were themselves the direct progenitors of 

 Conifers : they are too specialized — the fructifications of Cor- 

 daiteae, for example, were decidedly more advanced than those of 

 Araucarian Conifers. The plants from which, on this hypothesis, 

 the Conifers were derived were perhaps less highly modified than 

 the true Cordaiteae, such as Grand 'Eury and Renault investigated, 

 though still very advanced types. 



If, again, the Conifers had a mixed ancestry (not that I regard 

 such a view as really tenable), they could claim kindred partly with 

 the morphologically highest, partly with the most dominant race 

 of the earlier period. 



Thus, on any view, Dr. Gaskell's hypothesis finds support. 



The Grinkgoales, a group of some importance in Mesozoic ages, 



* " Pteropsides cles Temps Paleozoiques," Archives des Sci. Pliys. et Nat. 

 t. XX vi. 1908, Geneva. 



