xxxiv SCIENCE PROGRESS. 



" The things, we know, are neither rich nor rare, 

 But wonder how the devil they got there." 



This chapter contains, among other things, some interesting details 

 of the processes of silicification and calcification on which the preserva- 

 tion of vegetable remains with structure depends. The author justly 

 lays stress on the extraordinary perfection with which histological 

 structure is often preserved, a point never realised except by those who 

 have themselves examined good specimens. Mr. Seward is convinced 

 that in certain favourable cases even the nuclei of the cells are to 

 be recognised. 



Chapter v., on difficulties and sources of error, is very salutary, 

 though "the description of a fragment of the handle of a wedgewood 

 teapot as a curious form of Calamite " (p. 94) was no doubt an extreme 

 case ! The author justly insists on the uncertainty of characters drawn 

 from the form and venation of leaves. In fact, external characters 

 generally, when unsupported by evidence from structure, are only to 

 be used with the greatest caution. 



Chapter vi., on nomenclature, is commendably short, and free from 

 pedantry. 



This brings us to the main part of the book, the systematic ex- 

 position of the families of fossil plants. This is very fully done, and 

 gives proof of much research, and of sound criticism, based on personal 

 examination of the actual specimens. 



Mr. Seward's remarks on fossil Bacteriology, a subject of which a 

 good deal has been heard lately, are much to the point. We quote one 

 sentence : " Specialists tell us that the accurate determination of 

 species of recent Bacteria is practically hopeless ; may we not reason- 

 ably conclude that the attempt to specifically characterise fossil forms 

 is absolutely hopeless ? " (p. 138). 



Among the Algae the author calls attention to the valuable evidence 

 for the geological history of the Calcareous Siphoneae, which present a 

 marked contrast to other so-called fossil Algae, most of which are not 

 Algae at all. 



As regards the Bryophyta the fossil evidence is still almost en- 

 tirely negative. 



It is when we reach the Pteridophyta that the serious interest of 

 fossil remains for the botanist begins. Among the Vascular Crypto- 

 gams and Gymnosperms it is not too much to say that the value of the 

 fossil evidence to the comparative morphologist equals that from the 

 recent plants themselves. 



The botanical student will at once be struck by the presence of 

 four instead of three main divisions of Pteridophyta. The fourth 

 group — Sphenophyllales — is entirely fossil, and in fact only known at 

 present from the Palaeozoic rocks. 



Among the Equisetales the structure of the recent genus is first 

 described (no doubt for the benefit of geological students), and then the 

 fossil forms are taken in order, beginning with those nearest the living 



