1905] CURRENT LITERATURE 305 
PENHALLOW’S has recently published the first and general part of an extensive 
treatise on the anatomical determination of the North American Coniferales 
as well as certain species from Japan and Australia. The memoir represents 
the results of a quarter of a century’s work in this field andis of great importance 
from the paleobotanical and phylogenetic standpoints. Although the author 
expresses his appreciation of the value of a general anatomical study of the group, 
he limits himself to the structural features of the ligneous cylinder, for the reason 
that coniferous remains are ordinarily best preserved as fragments of wood. 
Wood structure is discussed under the following headings: spiral tracheids; 
bordered pits, distribution and structure; medullary rays; resinous tracheids 
and resin cells; and resin Passages. 
Under the caption of bordered pits, the author points out that multiseriate 
and crowded pits deforméd by mutual pressure are characteristic of the older 
8ymnosperms, the Cycadofilices, Cordaitales, etc. Bordered pits are in general 
confined to the radial walls of the tracheids, exceptions to this mode of distri- 
bution occurring only in the primary wood and in the autumnal tracheids of the 
annual rings. Under the heading of medullary rays, the various types of struct- 
ure which are of diagnostic importance are clearly and definitely described, and 
in this respect the present work marks a long advance on its predecessors. Two 
types of ray are distinguished, namely the linear ray made up of a single series 
of cells, and the more complex fusiform ray, which is so broad as to contain a 
horizontal resin canal. Resinous tracheids are described as diagnostic for the 
Araucarineae, but also occur sporadically in certain species of Abies. Resin 
cells, according to the author, appear in the more primitive conifers (exclusive 
of the yew-like Taxineae) and are characterized by their scattering, zoned, or 
Segregated distribution, the latter condition being considered the most specialized. 
Where the resin-cells are highly segregated they may give rise schizogenously 
to resin cysts of limited extent, with walls constricted at intervals. Resinous 
cysts are found characteristically in the abietineous genera Tsuga and Abies, 
but also occur in living and extinct Sequoias. In the abietineous genera Larix, 
Pseudotsuga, and Picea, the resin spaces form a continuous system of vertical 
and horizontal passages, which according to the author betray their derivation 
from resin cysts by the constricted character of their walls. In Pinus the resin 
Passages no longer show signs of constriction and are moreover lined entirely 
with thin-walled epithelium. 
The author, as the result of plotting frequency curves based on the occurrence 
of the various characters of the wood, reaches certain conclusions as to phylogeny 
which may be briefly stated as follows: The Taxaceae are the oldest of the Con- 
iferales, and from their general plexus have branched off on the one hand the 
Podocarpeae, and on the other the common trunk, which gave rise to the Taxo- 
ee 
"3 PENHALLow, D. P., The anatomy of the North American Coniferales together 
With certain exotic species from Japan and Australia. Part I. American Nat. 38: 
743-273, 331-359, 523-554, 691-723. 1904. 
