From the Complex to the Simple 203 



and with Isoetes if derived from Lepidodendreae), or the higher 

 branches of the family were crowded out altogether and only the 

 "poor relations" were able to maintain their position by evading 

 the competition of the ascendant races ; this is also illustrated by 

 the history of the Lycopod phylum. In either case there would result 

 a lowering of the type of organisation within the group. 



2. The course of real progress is often from the complex to the 

 simple. If, as we shall find some grounds for believing, the Angio- 

 sperms came from a type with a flower resembling in its complexity 

 that of Mesozoic " Cycads," almost the whole evolution of the flower 

 in the highest plants has been a process of reduction. The stamen, 

 in particular, has undoubtedly become extremely simplified during 

 evolution ; in the most primitive known seed-plants it was a highly 

 compound leaf or pinna ; its reduction has gone on in the Conifers 

 and modern Cycads, as well as in the Angiosperms, though in different 

 ways and to a varying extent. 



The seed offers another striking example; the Palaeozoic seeds 

 (if we leave the seed-like organs of certain Lycopods out of conside- 

 ration) were always, so far as we know, highly complex structures, 

 with an elaborate vascular system, a pollen-chamber, and often a 

 much-differentiated testa. In the present day such seeds exist only 

 in a few Gymnosperms which retain their ancient characters — in all 

 the higher Spermophytes the structure is very much simplified, and 

 this holds good even in the Coniferae, where there is no counter- 

 vailing complication of ovary and stigma. 



Reduction, in fact, is not always, or even generally, the same 

 thing as degeneration. Simplification of parts is one of the most 

 usual means of advance for the organism as a whole. A large pro- 

 portion of the higher plants are microphyllous in comparison with 

 the highly megaphyllous fern-like forms from which they appear to 

 have been derived. 



Darwin treated the general question of advance in organisation 

 with much caution, saying: "The geological record... does not extend 

 far enough back, to show with unmistakeable clearness that within 

 the known history of the world organisation has largely advanced 1 ." 

 Further on 2 he gives two standards by which advance may be 

 measured: "We ought not solely to compare the highest members 

 of a class at any two periods... but we ought to compare all the 

 members, high and low, at the two periods." Judged by either 

 standard the Horsetails and Club Mosses of the Carboniferous were 

 higher than those of our own day, and the same is true of the Meso- 

 zoic Cycads. There is a general advance in the succession of classes, 

 but not within each class. 



1 Origin of Species, p. 308. 2 Ibid. p. 309. 



