JANUARY 12, 1912] 
be severe from the observation of the sun- 
spots.” 
A hasty survey of the literature concerning 
the occurrence of Puccinia, and brief corres- 
pondence or personal conferences with some of 
our American botanists failed to reveal any 
knowledge of this hypothesis, and although it 
is not probable that it is of any great im- 
portance, I thought it would be of sufficient 
interest to be placed on record in an Ameri- 
can publication. CO. Stuart Gacrer 
BROOKLYN BOTANIC GARDEN 
SPECIAL ARTICLES 
TIER-LIKE ARRANGEMENT OF THE ELEMENTS OF 
CERTAIN WOODS 
THERE are numerous woods which present 
on longitudinal section (particularly the tan- 
gential) fine, delicate cross lines or stripes 
sometimes called “ripple marks.” The dis- 
tance between these markings varies from 
0.11 to 0.50 mm., and is fairly constant for a 
species. On some woods (e. g., Asculus 
octandra Marsh., Swietenta mahagoni Jacq., 
Bombax insigne Wall. and Pterospermwm 
diversifoliwm Blume.) these lines are very 
clear and distinct to the unaided eye; on 
others (e. g., Tilia americana L., T. pubescens 
Ait., Pterocarpus indicus Willd. and P. dal- 
bergioides Roxb.) they are near the limit of 
vision or again (e. g., Guaiacum sanctum L. 
and G. officinale L.) they are invisible with- 
out the lens. In most species showing these 
markings the feature is constant and of con- 
siderable importance for diagnostic purposes, 
though in a few species (e. g., Swietenia 
mahagoni) the same piece of wood may show 
the markings in one place and not in another. 
This cross-striping of a wood is due (1) to 
the arrangement of the rays in horizontal 
series, or (2) to the tier-like ranking of the 
wood fibers, vessel segments or other elements, 
or (3) to a combination of (1) and (2). The 
lines resulting from the horizontal seriation 
of the rays is usually more conspicuous and of 
more common occurrence than those in (2). 
In the combination of the two forms, which 
is very common, the junction of the vessel 
SCIENCE 
75 
segments or of the fibers is usually between 
the rays. 
This peculiar arrangement of wood ele- 
ments is also evidenced on transverse section. 
Where the rays are in perfect horizontal seria- 
tion a section between two tiers shows an 
entire absence of rays. In most instances, 
however, it results in gaps of irregular width 
depending upon the regularity of the stories. 
Where the rays are much wider near the 
middle than at the margin their apparent 
width when viewed transversely will show con- 
siderable variation, according to the relative 
location of the plane of section. Where the 
fibers are arranged in tiers their apparent size 
is affected in a similar manner. According to 
von Hoéhnel* the fibers in Bocoa provacensis 
Aubl., and a few other tropical woods with 
eross-striping are also radially disposed, and 
when the plane of cutting passes near the 
Junction of two tiers the section shows large 
and small cells in alternate radial rows. The 
small cells are sections of the tips of the fibers 
forced by growth between their upper and 
lower neighbors. It is von Héhnel’s theory 
that their appearance in alternate radial rows 
instead of alternately in the same row is the 
result of the pressure of the bark upon the 
cambium while the fibers were being formed. 
Tier-like arrangement is most common in 
tropical woods and has been found fairly 
characteristic of the families Osalpiniaces 
and Zygophyllacee. 
Various writers’ have 
+Von Hohnel, Franz Ritter, ‘‘ Ueber stockwerk- 
artig aufgebaute Holzkérper,’’ Sitzungsberichte 
der Mathematische-Naturwissenschaftlichen Classe 
der kaiserlichen Akademie der Wissenschaften, 
Vol. 89, Part 1, Wien, 1884, pp. 30-47. Von 
Hohnel, Franz Ritter, ‘‘Ueber den etagenformigen 
Aufbau einiger Holzkorper,’’ Berichte 
Deutschen Botanischen Gesellschaft, Vol. 
Berlin, 1884, pp. 2-5. 
2Flickinger, J. A., ‘‘Pharmacognosie der 
Pflanzen,’’ 2d ed., pp. 463, 466. Wigand, A., 
‘<Anatomische Atlas zur pharmaceutischem Werk- 
ende,’’ 1865, tables 26, 27. Whitford, H. N., 
‘(The Forests of the Philippines,’’ Bul. 10, Bu- 
reau of Forestry, Manila, P. I., 1911, Vol. IL., p. 
36. 
der 
ile, 
