No. 535] 



NOTES AND LITERATURE 



443 



the earlier formations. It is highly probable that in spite of 

 their simple structure the Diatoms are really comparatively re- 

 cent types. Their enormous numbers and practically universal 

 distribution at the present time, indicate that they are admirably 

 adapted to existing conditions. They particularly abound in the 

 Arctic and Antarctic seas. 



While the Fungi are rarely preserved in a very satisfactory 

 condition, there is abundant evidence of their presence in the 

 Paleozoic rocks. 



The geological history of the Bryophytes is in a very unsatis- 

 factory condition. Of the liverworts only a few impressions are 

 recorded, and these, according to Seward, are all from Mesozoic 

 or Tertiary formations, and so closely resemble the living species 

 that they throw no light upon the early history of the group. 

 Very few fossil remains which can with certainty be referred to 

 the true mosses are known, but the possibility of confusing the 

 remains of mosses with small Lycopods or even fragments of 

 coniferous branches has to be taken into account. 



It has been suggested that the very small number of unmis- 

 takable Bryophytes which lias been recorded in a fossil state 

 might be explained in the same way as wo have suggested for 

 the absence from the Paleozoic rocks of Diatoms; hut the cases 

 are hardly parallel since the Bryophytes, particularly the liver- 

 worts, give every evidence of being old and generalized types, 

 and do not appear to be particularly well adapted to modern 

 conditions, except as these duplicate what we may assume to 

 have been the conditions during the Carboniferous. It is only 

 in the extremely moist, even climate of the mountain tropics, 

 where the other Paleozoic type, the Pteridophytes reaches its 

 greatest luxuriance, that the liverworts form a conspicuous 

 feature of the flora. Moreover, the liverworts are far less 

 plastic, the number of species, even of wide-spread genera (ex- 

 cept in the leafy forms) being usually very small. Both their 

 distribution and their structures point unmistakably to their 

 being a primitive group. 



The absence of liverworts from the early geological forma- 

 tions can most readily be explained on the score of their great 



nizable form. Even were we to admit that tin- liverworts are 

 modern types, we should still have to explain why their progeni- 

 tors, and the presumably similar progenitors of the ferns, have 



