RELATION OF PLANT PROTOPLASM TO ENVIRONMENT. 269 



stable. Setchell well remarks in the paper already quoted: "We find that 

 when a proteid, like egg albumen, is free from water, it does not coagulate at 

 the very highest temperatures which leave it unburned, and that the less the 

 content of water, the higher the temperature of coagulation. ' ' The most resistan t 

 plant parts are undoubtedly those in which abundant protoplasm, with or without 

 stored protein or other food stuffs, fairly well fills the cell. Such cells or cell 

 aggregations show a wide range of biological possibilities in relation to environ- 

 ment. 



The views set forth above may be summarized as follows: 



1. Plant protoplasm may show a degree of temperature adaptability that 

 may range at least from - 200° C to + 100° C. 



2. The most ancient, and in structure most primitive plants are probably the 

 Schizophyceae (Cyanophyceae) , which may have originated during the Mid 

 Archaean or Proterozoic epoch, and were probably active agents then, as now, 

 in forming the siliceous and calcareous beds encountered in the strata of that 



period. 



3. The representatives of that group now living in hot springs and thermal 



waters, seem to be direct or little altered derivative species from the ancient 

 or Archaean types, and no good reasons can be advanced for viewing them as 



adaptive or acclimated from more cool and temperate species. 



4. They, like all thermo-resistant plant structures, have a rich and relatively 

 dense protoplasm, or a stored mass of reserve material with it in the cells, that 

 contribute to their thermo-resistant qualities. 



5. The above qualities are aided when mucilaginous walls or cell contents, 

 or thick and pigmented cellulose or ligin or cuticularized walls, exist in the above 

 group, or in any division of the higher plants, since these act as insulators and 

 equilibrators against over-rapid environmental action. 



6. That the thermophilic bacteria also represent an ancient series, either 

 derived from the Schizophycese by disappearance of the synthesizing cell pig- 

 ments, or arising independently by utilization of energy from sulphur or siliceous 

 compounds. These like the Schizophyceae have been active in the formation of 

 extensive rock masses of a sulphurous or ferruginous kind. 



7. That from the almost assuredly verified deposit of extensive siliceous, 

 calcareous, sulphur and iron rocks by one of the above two groups in late Archaean 

 times and on to the present day, we have strong suggestion that the Schizophyceae 

 and Schizomycetes represent primeval groups whose rock-forming activities have 

 been and are shown, where surroundings are favorable. 



8. That all physico-chemical, geological and biological knowledge point to 

 the conclusion that thermal spring action was once greatly more extended than 

 now, but that the restricted areas which now show it do not seem to differ in 

 their relations, their deposits, and probably in their organisms, from those of 

 ancient geologic origin. 



9. That the molecular composition, chemical activities, high energizing 



