JuLy 19, 1923 RYDBERG: NEW GENUS OF SENECIOID COMPOSITES 287 
operation the reflections from the stationary bead are observed through 
a low power microscope or binocular magnifying 25 to 50 diameters. 
The various phenomena described by Galibourg-Ryziger are shown 
equally well by this method. The preparation of beads of different 
sizes to fit different holes is a matter of only a few minutes. 
This method has the advantage over the first two methods in that 
it may be used to distinguish between normal pearls and cultivated 
pearls with a pear! center. 
In any case, test by all three methods should be applied, the one 
to serve as a check on the other. These tests are not time-consuming 
and in most instances lead to definite results. 
4. Test in ultraviolet light. Recently C. 8. Fox (Journ. Indian 
Industries and Labor, 1%: 235; Chemical News, 125, 67-68. 1922) 
has found that in ultraviolet light both natural and cultivated 
pearls fluoresce, with the difference, however, that the Persian Gulf 
pearls are opaque to ultraviolet light whereas Japanese pearls, both 
natural and cultivated, have a translucent opalescence. He considers 
that because the cultivated pearl has a nucleus which comprises from 
0.5 to 0.9 of the total volume of the pearl and which is of inferior 
material (mother-of-pearl) whereas a natural pearl is made up of con- 
centric layers of pearly substance from center to periphery, the culti- 
vated pearl is an inferior article and is not to be considered in the class 
with natural pearls. In view of the difficulty in distinguishing culti- 
vated pearls from natural pearls, he proposes that all Japanese pearls, 
both natural and cultivated, which show a translucent opalescence in 
ultraviolet light, shall be considered of inferior quality. The writer 
has repeated the test of Fox with the new fluorescent microscope of the 
Bausch and Lomb Optical Company and has noted that the translucent 
opalescence described by Fox is not so clearly and distinctly shown that 
uncertainty may not arise regarding the kind of pearl under test, 
whether Indian or Japanese. It would seem unwise to adopt this 
suggestion because pearls may at some future time be cultivated in the 
waters of the Persian Gulf and then the rule would fail to accomplish 
the desired result, and produce confusion worse than ever. 
BOTANY.—A new genus of senecioid composites. P. A. RYDBERG, 
New York Botanical Garden. (Communicated by Paut C. 
STANDLEY. ) 
The genus Clappia, named after Dr. A. Clapp of New Albany, 
Indiana, was described by Dr. Gray in the Botany of the Mexican 
Boundary Survey. Dr. Gray placed the genus in the tribe Helenieae, 
