50 
8. Annularia, with six species, having twenty synonyms, 
and including plants previously referred to six other 
genera. 
The ninth genus, AphyH/ostachys, is altogether doubtful. 
It needs indeed a bold systematist to attack such a 
chaos as this reveals, and an able one to deal with it 
effectively and well. 
The work will consist of three parts :—(1) an introduc- 
tion; (2) a botanical classification of all known fossil 
plants ; (3) a synopsis of them in geological sequence ; 
with a Bibliographical Index. 
The introductory part is very full, and is comprised jin 
ten chapters :— 
Chap. I.—Historical sketch. 
Chap. IJ.—On the state of preservation of fossil plants. 
Chap. I11.—Distribution of fossil plants in different formations. 
Chap, 1V.—Different modes of preservation, 
Chap. V.—Principles to be followed in the determination of 
ossil plants. 
Chap. VI.—Of the changes which have taken place in the 
vegetable kingdom from its first appearance up to the present 
time. 
(§ 1.) Disappearance of species ; 
(8 2.) The renewal of floras by the appearance of new types. 
Chap. VII. General coup d’ail of the floras of different 
geological periods, 
(1.) First epoch. Reign of the Thalassophytes.—(2.) Second 
epoch, Reign of the vascular Cryptogams.—(3.) Third epoch. 
Reign of the Gymnosperms. Appearance of Monocotyledons.— 
(4.) Fourth epoch. Reign of the Angiosperms. (a) First 
period ; Apetalous plants. (4) Second period ; Dialypetalous 
plants. (c) Third period ; Gamopetalous plants. - 
Chap. VIIT.—Application of vegetable paleontology to the 
climatology of the old world. 
Chap. IX.—Application of vegetable paleontology to geology. 
Chap. X.—General classification of stratified rocks. 
Of the above chapters, the sixth, which deals with the 
renewal of floras by the appearance of new types, will be 
the first to be read by many, naturally eager to ascertain 
the views of so able and so unprejudiced a naturalist as 
Prof, Schimper, on the subject of the Origin of Species. 
In this matter his views are explicit, and he sums up his 
reasons for adhering to the doctrine of evolution in the 
following terms :— 
In spile, then, of the deficiency of palmontological docu- 
ments, we cannot mistake the general line which Nature has 
followed through the various geological epochs, from the first 
appearance of organic beings to the period of their present 
development. ‘This line may be termed one of evolution, because 
it marks a progressive change from inferior to superior, from 
simple to compound, precisely similar to that of every individual 
with a complicated organisation. All agree that the latter is the 
yesult of a continued series of metamorphoses. Every erganised 
being begins as a simple cell ; the embryo itselt being a complex 
organism derived from the generating cell; wherefore there are 
naturalists who trace the individual back to the cell. We know, 
in fact, that each living vegetable cell can give birth to a new indi- 
vidual, of which it is in a certain sense the first representative. 
Many species of vegetables and animals do not rise above this simple 
cell; as soon as this has given birth to a second cell, the latter 
becomes in its turn a fresh individual. Whenever the derived 
cells remain united, so that a sort of solidarity is established 
amongst them, the being which is born from this agglomeration 
is a complex being. It will be so much the more perfect, it will 
occupy a step so much the higher in the scale of organisms, as 
the differentiation of functions produced by the metamorphosis of 
the cells is mere complete, and the organs applicable to these 
functions are more independent of each other. 
Has Nature followed this plan in her organic kingdom? From 
all that we know, I believe that we are justified in such a con- 
clusion, The only unicellular fossil plants with which we are 
acquainted are the Diatoms, which have left their siliceous shells 
NATURE 
[Mov. 11, 1869 
in the most ancient of fossil beds. The cellular plants of the 
family of Alga are doubtless rare in the palzeozoic formations ; 
with the exception of some little epiphytal fungi, no terrestrial 
cellular plants have been discovered, either in palzozoic or in 
mesozoic beds ; this class is even but meagrely represented in the 
tertiary flora, which has nevertheless much affinity with that of 
the present day. Nevertheless, these scanty remains suffice to 
convince us that, if the cellular plants which were to prepare for 
the arrival of vascular plants have not left numerous and striking 
traces, they have none the less existed, and doubtless since 
the earliest periods. ‘The first vegetation on the lands which had 
just appeared above the waters must have been composed of 
cellular “plants, of Confervae, of /rocmbryos or prothalliums of a 
lower or higher order of Cryptogams, as may be seen at the 
present day on recently reclaimed land, 
The terrestrial vegetation of the Silurian epoch and of the 
commencement of the Devonian having left no trace, it is impos- 
sible for us to judge what were the forms of the plants which 
then covered the reclaimed land. All that we know is, that the 
primeval ocean was peopled by a numerous fauna during thousands 
of centuries before the appearance of vascular cryptogamic acro- 
gens: similarly, if the Thalassophytes of those distant epochs 
had left no trace, their existence would be none the less infallibly 
proved by that of the animals whose food they formed. 
The rapid glance which we are about to give of the general 
character of the floras which have succeeded each other on the 
surface of the earth, from the Devonian period up to the present 
time, will show better than any reasoning the progressive march 
which they have followed, snd the close links by which they are 
united to each other, 
J. D. HooKErR 
HARCOURT AND MADAN’S PRACTICAL 
CHEMISTRY 
Exercises in Practical Chemistry. By A. G. Vernon- 
Harcourt, M.A., F.R.S., Sec. C. S.; and H. G. Madan, 
M.A., P.C.S., Fellow of Queen’s College, Oxford. 
Crown 8vo., pp. 350, 66 woodcuts ; 7s. 6d¢. (Oxford; 
Clarendon Press, 1869.) 
Wwe are glad at last to welcome a really scientific 
work on Practical Chemistry. Professor Harcourt 
and Mr. Madan have earned the warm thanks of all in- 
terested in the teaching of the science by the publication 
of their volume. Almost all former works on practical 
chemistry have been contented either to act the part of 
illustrated catalogues of chemical apparatus, or else they 
consist of cut and dried receipts for following out a system 
of qualitative analysis by reference to a complicated series 
of paragraphs, ingeniously arranged to bewilder the un- 
fortunate student as much as possible, or they place in 
his hands tabular statements of reactions which have to be 
worked through almost always without rhyme or reason. 
Mr. Madan’s Ten Commandments, or “ Memoranda,” 
placed at the commencement of the volume, might well 
be printed in letters of gold in every laboratory, and 
repeated as the morning lesson of each first year’s student. 
“Cleanliness,” he begins, “stands at ¢he head of the 
chemist’s scale of virtues.” No better advice can be given: 
if a student can work neatly, he is almost sure to work 
well. Only rarely can the “messy” beginner be trained 
to habits of exact experimentation and accurate thought. 
The second ordinance is equally important: “Do not 
work in a hurry. What is expended in time is often 
gained in power and grasp of a subject. Yet, on the 
other hand, learn to be economical of time.” The main 
object of a certain class of students seems to be to get 
“through” with their experiments, no matter how clumsily 
they manipulate, or how small and incomplete may be 
their knowledge of what the experiment teaches. They 
are satisfied to have “done the thing,” and if they do not 
