442 



THE AMERICAN NATURALIST 



[Vol. XLV 



look for the ancestors of the modern seed-bearing plants, the 

 rich pteridophytic flora of the Carboniferous naturally takes 

 first place, and it can be readily understood that an absorption 

 in the study of these interesting fossils should perhaps over- 

 shadow the importance of other forms. One can not help feeling 

 that if the search for remains of the Bryophytes in the Paleozoic 

 rocks had been pursued with the same zeal as has been shown in 

 the study of the vascular plants, something more than the ex- 

 tremely fragmentary evidences of their existence would be forth- 



Professor Seward, in his first volume published in 1898, has 

 given an admirable account of the different methods of fossiliza- 

 tion, and also the distribution of fossils. He points out in a very 

 interesting and convincing way the evidences of the existence 

 of the same factors at work at the present day as in times past. 

 Perhaps the most striking fact brought out in the distribution 

 of plant remains is the at first puzzling occurrence of fresh- 

 water and land plants in deposits of evident marine origin. Pro- 

 fessor Seward, however, shows that the great rivers of to-day, 

 like the Amazon and the Mississippi, are carrying out to sea 

 rafts of vegetation which may very well at some distant time be 

 discovered as fossils covered by marine deposits, to puzzle the 

 geologists of that future epoch. 



The history of the fossil Thallophytes remains very much as it 

 was at the time Professor Seward's first volume was published, 

 a rather significant comment on the neglect of these important 

 plants when compared with the great advances made in our 

 knowledge of the fossil Pteridophytes and Gymnosperms during 

 the past decade. 



As most of the Thallophytes. especially the alga?, are extremely 

 delicate and perishable organisms, the rarity of recognizable 

 fossil remains is not to be wondered at. Where there is a cal- 

 careous incrustation, as in the coralline alga; and many 

 Siphonete, very perfect fossils have been preserved. The latter 



portant role as reef -builders. 



Among the most characteristic of fossil plants are the Diatoms, 

 mile these have left enormous deposits of their flinty shells in 

 the Cretaceous and later rocks, they are practically unknown in 



these Siphones can be 

 order is evidently a ver; 



