248 PLANT-LIFE 



may be assured that living protoplasm is fully capable 

 of response, and that in Life itself there are potentialities 

 which will lead to wonderful results. 



In concluding this chapter, we have to make a brief 

 note concerning fossil remains of some of the lower and 

 humbler plants. It has been claimed that traces of 

 Bacteria have been detected in association with other 

 plant fossils, even in those of Carboniferous Age, but the 

 evidence for the claim is not sufficiently convincing. 

 Diatoms have been traced back to the Jurassic. They 

 are plentiful in Cretaceous and Cainozoic strata. Their 

 siliceous shells lend themselves to preservation, and if 

 they had been an ancient type of plant, we might cer- 

 tainly expect to find them at least as far back as the 

 Palaeozoic. The fact that we do not find them until the 

 Upper Mesozoic suggests that they are by no means 

 primitive, but a distinctly late product of plant-life. 

 Remains of Seaweeds are attributed to Silurian times, 

 but many impressions on rocks, claimed by some to 

 represent Seaweeds, fail to carry conviction to the un- 

 prejudiced mind. Coralline Seaweeds, coated as they 

 are with calcareous matter, lend themselves to fossiliza- 

 tion, and many such are found fossil in Mesozoic and 

 Cainozoic strata. The Characeaa, a curious and anoma- 

 lous group of water plants found in ditches, brackish 

 water, ponds, etc., and known as Stone worts, are crypto- 

 gams. They deposit calcareous matter in their cell- 

 walls, and hence are also good subjects for fossilization. 

 Their stems and also spore-fruits are found fossil in 

 Cainozoic strata. The lower Fungi are detected in con- 

 nection with Carboniferous plants, their hyphae being so 

 excellently preserved in petrifactions that they can be 



