258 RECORD: STRUCTURE OF CERTAIN WOODS 
phyllaceae (only a few woods of which were studied), in which all 
of the woods are characterized by horizontal ranking of their 
elements. In many cases it appears to be a generic character but 
more often it is specific only. A few instances have been noted 
where the feature is not constant for a given species and may be 
of only local occurrence in the same specimen. One of the best 
examples of this is furnished by Swietenia, where ‘“‘ripple marks”’ 
exhibit wide variation in regularity and occurrence and are about 
as likely to be absent as present. In general, however, the con- 
stancy of the feature seems to bear a direct relation to the degree of 
regularity of the cross-markings. It is most dependable when all 
of the elements are involved and especially when the rays are fine 
ahd of uniform height. 
In this investigation attention has been given to the elements 
storied, the regularity and visibility of the transverse markings and 
to the height of the tiers in each wood examined. In most in- 
stances only the gross and lens characters are given since they are 
most readily employed in practice. There are so many factors 
entering into the question of distinctness or visibility that the 
particular observations of the writer may not always apply. For 
instance, in Guaiacum the markings, though extremely fine, are 
distinct under the lens in the sapwood and may be indistinct or 
even invisible in very resinous heartwood. Usually the visibility 
is materially increased by moistening the surface, but in some in- 
stances the opposite effect is produced. 
According to Von Hohnel (2, p. 2) the distance between the 
cross-lines varies from one half to one eleventh of a millimeter, 
and for a given species is constant. In order to determine 
whether or not there is a definite tier-height for each species the 
present writer counted the number of tiers per inch of length on 
the tangential section of every specimen examined. An inch, 
divided into quarters, was marked off and the count and recounts 
made under the lens for the entire inch, the quarter-marks serving 
as an additional check. In the larger specimens, at least two dif- 
ferent inches were counted. In some instances the markings, be- 
ing fairly distinct without a lens but indistinct with it, were 
counted with the naked eye or with the aid of a reading-glass. 
Where the rays are not in seriation the cross-lines are likely to be 
