60 4 BOTANICAL GAZETTE [JULY 
rule appreciates the standpoint of the other. The first chapter contains a 
brief historical sketch of paleobotany, in which the author gives special credit 
to Brongniart and Williamson. Chapter two gives the relation of the sub- 
ject to botany and geology. Professor Seward tells how paleobotany has 
been buffeted about by the geologist and the botanist, the one culling out 
facts relating to the correlation of strata, the other caring only for facts which 
give hints as to phylogeny and evolution. He pleads for the recognition of 
paleobotany as a science of and for itself, with its own peculiar problems, 
viz., the determination of the historical succession of plants in geological 
time; the delineation of the actual evolution of the plant kingdom, giving 
light on phylogenetic mysteries ; the presentation of the various floral areas 
of the past, leading up to an explanation of the distribution of plants in the 
present day; conclusions as to climatic and other conditions in geological 
time, as revealed by the occurrence of certain peculiar plant types and by 
anatomical adaptations to environment. 
The third chapter gives the leading facts of geological history and is 
designed for botanical readers. 
The next chapter discusses the various methods for the preservation of 
plants as fossils; structure unmodified, as in fossil soils and forests; carbon- 
ization; incrustation, as travertine; casts; petrifactions. The relative 
rarity of plant fossils is due to their soft structure and land habitats. Chap- 
ter five is exceedingly interesting and valuable, as it demonstrates the enor- 
mous difficulties and sources of error, such as (1) the danger of depending too 
much on external resemblances, since many forms from alge up to seed 
plants may look alike, even in modern forms, much more in fossils ; (2) frag 
mental preservation (this is much more common than in animal fossils, and 
also leads to much more error, since a plant often can be identified only 
in fruit); (3) the decorticated trunks and pith cylinders; (4) resemblance to 
animals or animal tracks and mineral deposits. 
After a chapter on nomenclature, the author takes up the plants by 
groups. In this first volume he treats only of the thallophytes, bryophytes 
and some pteridophytes. Among the alge there is an abundance of 
undoubted fossil blue-green alge, forming deposits of travertine and possi- 
bly oolite ; Professor Seward thinks that similar forms probably represented 
the first life of the Algonkian. Because of their siliceous tests there are vast 
deposits of diatoms, mainly from the Cretaceous on. Of the larger marine 
algae those forms are especially preserved which are covered during life by 
calcareous incrustations, especially the corallines. Many plants of all kinds 
and many mineral deposits, rill marks, and animal tracks have been referred — 
to the alge, and especially to the fucoids. Among the fungi there are 
abundant evidences of fossil bacteria, but the higher forms are rare, though 
found in the Carboniferous and Tertiary. The liverworts and mosses ae 
poorly preserved and difficult to identify. Of the pteridophytes, the author 
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