162 ANCIENT PLANTS 



the less chance has it of being preserved without decay 

 long enough to be fossilized. As will have been under- 

 stood from Chapter II, even when the process of fossiliza- 

 tion took place, geologically speaking, rapidly, it can 

 never have been actually accomplished quickly as com- 

 pared with the counter processes of decay. Hence all 

 the lower plants, with their soft tissue and lack of wood 

 and strengthening cells, seem on the face of it to stand 

 but little chance of petrifaction. 



There is much in this argument, but it is not a 

 sufficient explanation of the rarity of lower plant fossils. 

 All through the preceding chapters mention has been 

 made of very delicate cells, such as pith, spores, and 

 even germinating spores (see fig. 47, p. 68), with their 

 most delicate outgrowing cells. If then such small and 

 delicate elements from the higher plants are preserved, 

 why should not many of the lower plants (some of which 

 are large and sturdy) be found in the rocks? ' 



As regards the first group, the mosses, it is probable 

 that they did not exist in the Palaeozoic period, whence 

 our most delicately preserved fossils are derived. There 

 seems much to support the view that they have evolved 

 comparatively recently although they are less highly 

 organized than the ferns. Quite recently experiments 

 have been made with their near allies the liverworts, and 

 those which were placed for one year under conditions 

 similar to those under which plant petrifaction took place, 

 were found to be perfectly preserved at the end of the 

 period ; though they would naturally decay rapidly under 

 usual conditions. This shows that Bryophyte cells are 

 not peculiarly incapable of preservation as fossils, and 

 adds weight to the negative evidence of the rocks, 

 strengthening the presumption of their late origin. 



That some of the lower plants, among the very 

 lowest and simplest, can be well preserved is shown in 

 the case of the fossil fungi which often occur in micro- 

 scopic sections of palaeozoic leaves, where they infest 

 the higher plants as similar parasitic species do to-day. 



