872 LIFE : OUTLINES OF GENERAL BIOLOGY 



land introduced the new factor of atmosphere. This was the Xero- 

 phyte Epoch. In other words, we must think: (i) of the primal Open 

 Sea, with its free-swimming minute green plants; (2) of the floor of 

 the illumined shallow sea with its anchored fronds, with new experi- 

 ments in body-making on the one hand and in reproductive dispersal 

 on the other; and (3) of the beach slowly rising, foot by foot, 

 millennium after millennium, with its highly evolved seaweeds 

 slowly adapting themselves into land plants. 



"The energy of growth, at bottom a phase of chemical (ionic) 

 activity, supplies the driving-power of life, and such 'life' beats 

 against the sieve of Natural Selection ; but this alone does not account 

 for all the manifestations of plant-organisation. Twice in the history 

 of the world the sieve itself has been changed: the 'hidden hand' 

 which did this, and so determined the path to be taken as a sequence 

 of progression, was not 'Nature' or 'Divine Guidance', except in so 

 far as such expressions may be utilised to cover an inevitable march 

 of events, in this case merely the expression of the cooling of the 

 earth, which (i) lifted the sea-bottom, by tectonic changes, and (2) 

 ultimately lifted the 'land' above the surface of the water, to be 

 subjected to subaerial denudation to form 'soil'." Of course, only 

 a few of the plankton creatures would get through the sieve to 

 become anchored seaweeds on the substratum, and only a few of the 

 benthic plants through the new sieve, to become the pioneers of a 

 land flora. The idea of an evolution of sieves as well as an evolution 

 of the sifted material is useful, but we should not be inclined to 

 restrict the operations of the "hidden hand" to twice. 



It is very impressive to visit a rocky foreshore at the lowest tide, 

 to wade out among the Laminarian and other seaweeds not usually 

 exposed at all, to observe the vigour and manifoldness of their 

 growth and the complexities of their structure, and to realise that 

 one is moving amid an antique vegetation, some members of which 

 may be much older than the hills. The conventional view has been 

 that these seaweeds represent a gorgeous blind alley; but Dr. Church 

 compels us to consider the possibility that from among such highly 

 evolved creatures the land flora may have emerged by gradual 

 transformation as the foreshore slowly rose. This transformation 

 cannot be thought of in any easygoing way. It meant that the 

 seaweeds' gripping structures — mere holdfasts, not true roots at 

 all — became provided with rootlets and root-hairs suited for the 

 absorption of water and dissolved salts from the soil. It meant that 

 a frond-surface adapted for the absorption of watery food-solution 

 became fit for the absorption of the dry gases of the air. It meant 

 the elaboration of a complicated vascular system, for conveying 

 the raw materials and the elaborated materials from part to part. 

 These are among the more readily stated of the difliculties which 

 are faced — and ingeniously countered — by Dr. Church. 



