JANUARY 31, 1907 | 
NATURE 
AMERICAN FOSSIL CYCADS.' 
“THE wonderful state of preservation of many Palaozoic 
plants, which has enabled us to gain much valuable 
information in regard to phylogenetic problems, is in 
marked contrast to the general absence of petrified fossils 
afforded by Mesozoic strata. Thanks to the ability and 
energy of Mr. G. R. Wieland, liberally backed by the 
Carnegie Institution, a flood of light has been thrown on 
the morphology of an extinct group of Mesozoic gymno- 
sperms, which it is possible to study with a precision and 
thoroughness hardly to be surpassed in the case of recent 
plants. Mr. Wieland’s monograph, with its splendid set 
of large plates, is an addition to botanical literature of 
exceptional importance. After reading the volume, we 
couple with a grateful acknowledgment of what has already 
been done an earnest wish that the results of further in- 
vestigations may be presented in an equally attractive form 
in the near future. 
Mesozoic plant-bearing rocks in almost all parts of the 
world are characterised by an abundance of pinnate fronds, 
recognised by Brongniart and by other pioneers of palzeo- 
botany as cycadean on account of their close agreement 
in external characters with those of modern cycads—a 
small group of tropical gymnosperms occasionally extend- 
ing into subtropical regions, which constitute an un- 
obtrusive assemblage of survivals from a remote past. 
Stems which might reasonably be supposed to have borne 
these fronds have until recently been met with in a few 
localities only, and never in great quantity, except, perhaps, 
in the Purbeck beds of Portland. As Wieland says, it is 
with the work of the English botanists Carruthers and 
Williamson (1868) that the exact investigation of fossil 
cycadean stems “‘ may be said to have fairly begun.’’ The 
famous species Bennettites Gibsonianus of Lower Green- 
sand age, discovered many years ago in Luccomb Chine 
in the Isle of Wight, first described by Mr. Carruthers and 
afterwards by Prof. Graf zu Solms-Laubach, has made us 
familiar with the striking differences between the repro- 
ductive shoots of this extinct type and those of existing 
cycads, differences of surprising magnitude in view of the 
close resemblances as regards habit and vegetative anatomy. 
Other European examples of Bennettites have been de- 
scribed by Profs. Cappellini and Solms-Laubach, and an 
exceptionally well-preserved French Liassic species by Prof. 
Lignier, of Caen. In 1860 Philip Tyson discovered a few 
silicified cycadean stems in the Potomac formation of 
Maryland, but these were not submitted to more than a 
superficial examination; it was not until the last decade 
of the nineteenth century that the late Prof. Marsh, of 
Yale, with an energy worthy of a pupil of Goeppert, secured 
a collection of more than 7oo petrified stems from the 
Upper Mesozoic rocks of the Black Hills of Dakota and 
Wyoming. European botanists who have had an oppor- 
tunity of seeing some of these relics of cycadean groves 
of the Upper Jurassic and Lower Cretaceous periods in 
American museums have eagerly waited for the publication 
of Mr. Wieland’s investigations, and the preliminary 
papers which he contributed to the American Journal of 
Science (1899-1904) served to intensify the impatience with 
which the more complete descriptions have been awaited. 
In chapter i. the author gives an interesting summary of 
collections of cycadean stems; chapter ii. is devoted to 
their preservation and external characters. In chapter iil. 
we read of the difficulty of attacking these enormous 
flint-like fossils, and of the ingenuity by which the silicified 
trunks were made accessible to minute examination. 
Tubular drills were found to afford the best results; 
photographs of some of the drilled stems remind one of 
cylindrical cheeses to which the taster’s scoop has been 
freely applied. 
Chapter iv. treats of internal structure; many of the 
facts recorded merely confirm what was previously known, 
but additional information is given in regard to the anatomy 
of vegetative organs which makes us wish for further 
details in regard to many points still left in doubt or in- 
completely dealt with. We should like to know more 
about the relative abundance of centrifugal and centripetal 
1 “American Fossil Cycads"" By G. R. Wieland. Pp. viii+284+ 
pates. (Published by the Carnegie Institution of Washington, 19c6.) 
NO. 1944, VOL. 75 
wood in the leaf-traces; we are curious to know whether 
the Bennettites stems usually possessed one cambium-zone 
or several, and it would be interesting to have more 
definite statements as to the histological characters of the 
secondary wood. It is not improbable, as Mr. Wieland 
suggests, and as the writer suspected from an examination 
of a silicified cycadean stem from India, that these Meso- 
zoic stems, in some cases at least, differed from modern 
evycads in the greater compactness and hardness of their 
wood. No one recognises more fully than Mr. Wieland 
how much remains to be done, and he promises to do his 
best to fill up these and other lacuna. In chapter v. we 
have an exceedingly interesting account of the vernation 
and structure of young fronds preserved in buds on the 
main trunk. It is a curious fact that, despite the extra- 
Fic. 1.—Cycadeoidea Marshiana. Longitudinal section through ovulate 
strobilus. s=remnant of dehiscent disc of microsporophylls. 
ordinary abundance of stems, detached fronds have not 
been found in the enclosing strata, a circumstance which 
enhances the value of the discovery of unexpanded pinnate 
leaves in organic connection with the stem. 
It is, however, in chapters vi. and vii. that we find by 
far the most important part of the author’s work. The 
researches of Carruthers and other authors have shown 
that Bennettites did not bear terminal, or in some cases 
apparently terminal, flowers as.do the true cycads, but 
produced axillary branches consisting of a comparatively 
short axis ending in a terminal receptacle crowded with 
two sets of appendages, slender stalks terminating in 
single orthotropous seeds associated with sterile organs, 
probably homologous with the seed-bearing pedicels, termed 
interseminal scales, which overtopped the small seeds and 
almost completely enclosed them in a protecting envelope. 
These axillary shoots usually occur in profusion on a 
single stem, and, as Wieland points out, often in approxi- 
