September 27, 1912] 



SCIENCE 



415 



as by tlie method of comparison of averages 

 for all " odd " and " even " we find : 



By botli methods all the deviations are nega- 

 tive in sign, though of a low order of magni- 

 tude. Apparently, bean seeds produced in 

 pods with an odd number of ovules are about 

 .0025 gram lighter than those in pods with an 

 even number. Asymmetrical pods are, there- 

 fore, physiologically less efficient than sym- 

 metrical. To be sure the relationship is a 

 very delicate one; the individual series show 

 considerable fluctuations. Many more ob- 

 servations are desirable, but the duplication 

 of a series of over 23,000 individual weighings 

 with records of the characteristics of the pods 

 from which the seed was derived is not easily 

 carried out. The findings are consistent 

 throughout within the limits of error. They 

 confirm from an entirely different angle con- 

 elusions drawn from studies of selective elim- 

 ination and of fertility and fecundity. It 

 seems worth while, therefore, to place on 

 record the results for the available data. 



J. Arthur Harris 



Cold Spring Haeboe, N. T. 



heat conductivity op crystals 

 For several years one of the experiments in 

 our course in physical crystallography has 

 been a qualitative determination of the con- 

 ductivity of heat in crystals by the Senarmont 

 method described by Groth, " Physikalische 

 Krystallographie," page 178. The Senarmont 

 apparatus is used for these tests. It consists 

 of a stage for supporting the crystal, so ar- 

 ranged that a spring presses it up against the 

 contact point of the conductor. The latter is 

 bent at right angles and may be heated at the 

 other end by a flame. Results were quite un- 

 satisfactory because when the point, resting 

 on the parafiined surface of the crystal, be- 

 came heated it radiated sufficient heat to melt 



the paraffine and the figure, which might have 

 been obtained by heat conducted through the 

 crystal, was destroyed. Since the heat was 

 radiated equally in all directions a circle in 

 the parafiine resulted. A modification of this 

 method gives much better results. 



A plate of the mineral, for example, gypsum, 

 about 1-2 mm. thick is dipped in melted par- 

 affine until a thin even coat is formed on one 

 side. The plate is then placed on the stage of 

 the instrument with the paraffined surface 

 down, but is insulated from the stage by strips 

 of asbestos under the edges. The point of the 

 conducting wire rests in a depression in the 

 upper unparaffined surface. In this way, 

 when the heat is conducted along the wire to 

 the crystal it must actually be transmitted 

 through the gypsum before it can melt the 

 paraffine. A very sharply defined ellipse will 

 be noted in the paraffine and this is clearly 

 due to differences in conductivity of the gyp- 

 sum in different directions and not to radia- 

 tion from the wire. E. W. Clark 



MiNERALOGICAL LABORATORY, 



Univeksity OP Michigan, 

 May 30, 1912 



SOME CURIOUS CASES OP SELECTIVE REPLECTION 

 IN ULTRAVIOLET LIGHT 



Professor Woods, of Johns Hopkins Uni- 

 versity, has found that some white flowers, 

 when photographed in ultraviolet light, ap- 

 peared as black or nearly so. This fact led 

 the writer to examine the behavior, in such 

 circumstances, of a number of alkaloids, 

 glucosids and other vegetable immediate prin- 

 ciples he happened to have on hand. The re- 

 sult is shown on the two accompanying 

 figures. Photograph number I. was taken 

 with an ordinary objective. Number II. is a 

 photograph of the very same substances taken 

 with a quartz convex meniscus, silvered on 

 both faces and completely opaque to visible 

 light. The 24 substances had been previously 

 powdered and somewhat compressed into their 

 respective boxes. As the ordinary photograph 

 shows, they were, with but one exception 

 (berberin) perfectly white. Photograph num- 

 ber II. shows that, if our eye were sensitive 



