76 SCIENCE 
called attention to this feature which is espe- 
cially striking on red sanders (Pterocarpus 
santalinus L. f.), narra (P. indicus Willd.), and 
Jamaica quassia (Picrasma excelsa Planch.). 
Von Héhnel (Joc. cit.) observed it in about 80 
different woods, all tropical or sub-tropical but 
one (Diospyros virginiana L.), and most of 
them unidentified. His list of the identified 
woods includes 35 genera of 12 families, viz., 
Ozsalpiniacee, Papilionacer, Mimosacer, 
Zygophyllacez, Biittnereacer, Malvacez, Ced- 
relacee, Bignoniacexe, Simarubacex, Ebenacez, 
Rosacez and Sapindacee. 
Included in v. Hoéhnel’s list are two species 
which occur in the United States, viz., 
Swietenia mahagoni and Diospyros virgin- 
jana. In addition to these two the present 
writer has observed tier-like arrangement in 
the woods of Msculus octandra, Tilia ameri- 
cana, T. pubescens, T. heterophylla Vent. and 
Guaiacum sanctum. 
ZESCULUS (BUCKEYE) 
In the wood of @sculus octandra the rays 
are fine, uniseriate, uniform, inconspicuous, 
mostly 10-12 cells high, measuring about 0.25 
mm. The average distance between the rays 
is, vertically, 0.15 m.; laterally, 0.06 mm. 
Their arrangement is in horizontal series, 
very regular on the radial section but form- 
ing somewhat wavy lines on the tangential, 
though always plainly visible to the unaided 
eye. The vessel segments are from 0.35 to 
0.40 mm. long and are in series, the horizontal 
planes of their perforations alternating with 
the rays. The fibers appear not to be in 
storied arrangement. 
The cross-markings on tangential surface 
are characteristic of A. octandra and were 
not observed in A. glabra Willd., A. cali- 
fornica Nutt. or A. hippocastanum L., though 
all three show indistinctly on radial surface a 
tier-like arrangement of the wood elements. 
This feature is thus important in separating 
the wood of A. octandra from others of the 
genus. 
TILIA (BASSWOOD) 
Tier-like arrangement of the wood elements 
is characteristic of the woods of Tilia ameri- 
[N.S. Vou. XXXV. No. 889 
cana, T. pubescens and T. heterophylla. The 
ending of the vessel segments, wood fibers and 
wood parenchyma fibers is quite uniform. 
The rays are widely variable in size and are 
irregularly spaced. The small rays are uni- 
seriate and mostly 10-15 cells high; the larg- 
est are 3-5 cells wide and 50-100 cells high. 
The cells are small and much flattened later- 
ally. 
The cross-markings of Tilia are not con- 
spicuous, but in proper light are usually 
readily visible to the unaided eye. The aver- 
age height of the tiers is about 0.40 mm. 
SWIETENIA (MAHOGANY) 
Tier-like arrangement is often characteristic 
of the true mahogany (Swietenza mahagont). 
While it may be absent, it is quite often very 
conspicuous. When present the tiers vary in 
height from 0.35 to 0.50 mm. The rays are 
deep crimson in color, fusiform, and quite 
irregular in size; 1-5, mostly 2 or 3, cells wide, 
and 4-20, mostly 10-15, cells high. When 
the rays are in storied arrangement they coin- 
cide with the vessel segments. 
Swietenia senegalensis Deso. is said by von 
Hoéhnel (loc. cit.) to be without cross-striping. 
DIOSPYROS (PERSIMMON) 
In Diospyros virginiana the rays are very 
numerous, composed of large cells in 1-2 
(rarely 3) rows, and from 2-14, usually 10- 
12, cells high. They are arranged in hori- 
zontal series which correspond with the ves- 
sel segments, wood fibers and wood-paren- 
chyma fibers. The arrangement is often 
somewhat irregular and is never conspicuous, 
though clearly visible to the unaided eye. 
The height of the tiers is about 0.85 mm. 
The horizontal seriation of the rays appears 
to have been first described by Molisch.° 
Available specimens of the wood of D. tea- 
ana Sch. do not exhibit the cross-markings. 
®Molisch, H., ‘‘Vergleichende Anatomie des 
Holzes der Ebenaceen und ihrer Verwandten,’’ 
Sitzungsberichte der Mathematische-Naturwissen- 
schaftlichen Classe der kaiserlichen Akademie der 
Wissenschaft, Vol. 80, Part I., Wien, 1879. 
