Band 107. Nr. 18. 
XXIX. Jahrgang. I. Bd. Nr. 18. 
Botanisches Centralblatt. 
Referirendes Organ 
der 
Association Internationale des Botanistes 
für das Gesamtgebiet der Botanik. 
Herausgegeben unter der Leitung 
des Präsidenten: des Vice-Präsidenten: des Secretärs. 
Prof. Dr. R. v. Wettstein. Prof. Dr. Ch. Flahault. Dr. J. P. Lotsy. 
und der Redactions-Commissions-Mitglieder: 
Prof. Dr. Wm. Trelease, Dr. R. Pampanini und Prof. Dr. F. W. Oliver. 
von zahlreichen Specialredacteuren in den verschiedenen Ländern. 
Dr. J. P. Lotsy, Chefredacteur. 
No. 18. 
Abonnement für das halbe Jahr 14 Mark 
durch alle Buchhandlungen und Postanstalten. 
1908. 
Alle für die Redaction bestimmten Sendungen sind zu richten an Herrn 
Dr. J. P. LOTSY, Chefredacteur, Leiden (Holland), Witte Singel 26. 
Bower, F. O., The Origin of a Land Flora: a theory based 
upon the facts of Alternation. (Macmillan & Co. Ld. London. 
1908. 717 pp. 361 Figs. and Frontispiece.) 
The object of the author of this volume has been to present in 
detail the evidence which may be held to support the Biological 
Theory of Antithetic Alternation briefly stated by him in the Annals 
of Botany in 1890 (Vol. IV. p. 347,): and at the same time to examine 
those arguments which have from time to time been advanced in 
Opposition to it. It is held that the facts and arguments brought 
forward in this book give a reasonable basis of probability for its 
acceptance. The hypothesis is that the change of conditions of life 
involved in the invasion of the Land by organisms originally aquatic 
has played a prominent part in the establishment of those alterna- 
ting phases of the life-cycle which are so characteristic of Archego- 
niate Plants. Comparison indicates that their sporophyte originated 
as a phase interpolated between the recurring events of sexual fusion 
and chromosome-reduction in the life-cycle of water-livingorganisms: 
an amphibious condition was thus produced by an amplification of 
the diploid phase, and the sporophyte is regarded as having under- 
gone special development in relation to the production of numerous 
germs — the spores, — for the dissemination of which dry condi¬ 
tions are essential. In the simplest forms these spores are all alike, 
and the larger their number the greater the probability of survival 
of the type, and of its spread. In their high numbers there is found 
a set-off against the increased difficulty of zoidiogamic fertilisation 
which the Land-Habit entails. 
Botan. Centralblatt. Band 107. 1908. 
29 
