28 PKOCEEDINGS Or THE 



plant. AVithout going into details, I may say that the argument 

 rests on the relatively great deA'elopment of the pv-iwio)'?/ vascular 

 tissues in many Palaeozoic plants, on the frequent sharp distinc- 

 tion between primary and secondary formations, and on the late 

 appearance of the latter in the individual development. The 

 arguments do not apply with equal strength to all groups, and 

 the conclusion may not hold good universally. We know that 

 secondary growth occurs in seaweeds at the present day, and it 

 may quite possibly have existed even among the very earliest 

 land-plants, but in certain phyla it seems to have been a relatively 

 new character, though dating from times before the Devonian, 

 Supposing we could go back far enough, we might find a real 

 deiicieucy in respect of secondary growth, but its absence would 

 not imply defective adaptation (anymore than in Monocotyledons 

 at the present day) for there is a boundless variety in the ways in 

 which plants can equip themselves for the battle of life. 



The hypothesis of " a gradual development from the simpler to 

 the more complex " is not borne out by the facts of Palaeobotany 

 — the real course of events was infinitely more involved. On a 

 general view, as Darwin himself recognized, " The geological record 

 does not extend far enough back to show with unmistakeable 

 clearness that \A'ithin the known history of the World organisation 

 has largely advanced." * This wise saying has been too often 

 overlooked by those who have tried to popularize Evolution — it is 

 eminently true of the geological history of plants. Though there 

 is no doubt a balance on the side of advance, due chiefly to the 

 increasing complexity of the interrelations among the organisms 

 themselves, the general progress since Palaeozoic days is by no 

 means so great as has often been assumed, and we may be sure 

 that as our knowledge of the older plants increases, we shall come 

 to form a still higher estimate than we do now of their adaptive 

 organization. 



It has been alleged that it is the fact of the gradual appearance 

 of higher forms which enables us to determine the relative age of 

 strata by their fossils. So far as plants are concerned, this state- 

 ment is only true to a very limited extent. A fossil Angiosperm, 

 no doubt, would be evidence of an age not earlier than the Creta- 

 ceous, but on the other hand a Lycopod of much higher organiza- 

 tion than at present, would establish a strong presumption of 

 Palaeozoic age ; so would the higher forms of the Equisetales ; a 

 Cycadophyte with a fructification far more elaborate than that of 

 recent Cycadaceae would afford sure proof that the bed containing 

 it belonged to the Lower Mesozoic. 



Of course much depends on the meaning we give to the words 

 " higher" and " lower." If by " higher " we mean nearer to the 

 recent types, then it is merely a truism to say that the higher 

 forms are characteristic of the later rocks. But if by "higher" 

 we mean more elaborately differentiated, then the statement 

 quoted is, in any general sense, untrue. If again we imply by 



* ' Origin of Species/ 6th edition, p. o08. 



