ORIGINATION OF SELF-GENERATING MATTER 295 



moist conditions would be a process resulting in enormous loss of 

 species. Some spinose types would seem to offer the best morpho- 

 logical features for such a change. 



Perhaps the most inportant of all of the altered conditions brought 

 about by increasing moisture, however, would be the total trans- 

 formation of the competitive struggle for existence. Animals would 

 no longer play the predominating role as in arid areas. The num- 

 ber of individuals representing the constituent species of a flora 

 would be multiplied a hundred fold, perhaps a thousand fold, and 

 once more the amount of food material offered to animals would 

 decrease their total importance as a factor in selection, while the 

 intensest crowding between shoots would once more be resumed and 

 horizontal differentiation of associations such as that in forests 

 would ensue. 



The element of a desert flora which would respond most readily 

 to ameliorated aridity would, of course, be the hygrophytic annuals 

 and perennials, which had survived the period of desiccation in 

 their refuge of the rainy seasons, and in the moist areas along stream- 

 ways and on elevated peaks. These would quickly occupy the greater 

 part of the surfaces available for plants to the great intensification 

 of the inter-vegetal struggle for existence. As these hygrophytes 

 survived in the moist situations and the moist seasons of an arid 

 period, so the surviving xerophytes in a moist period would find 

 refuge in restricted habitats on talus slopes, rocks, and sand in which 

 the soil-moisture relations would be best suited to their specialized 

 structure and might display their seasonal activity during a period 

 of the year in which the precipitation was least. 



Briefly restating the principal ideas touched upon, it may be said 

 that Chamberlin's prothesis of the planetesimal aggregation of the 

 outer portions of the earth and the attendant conditions, together 

 with current theories as to the catalytic nature of the essential activi- 

 ties of protoplasm, makes possible rational speculations upon the 

 origination of self-organizing matter. 



The passing of nitrates, phosphides, carbides, and sulphides into 

 more stable combinations might readily result in the formation of 

 thermo-catalysts, one type of which survived in the later forms of 

 living matter. Similar combinations do not appear to be taking 



