Characterization of gibberellins from light-grown Phaseolus coccineus seedlings by combined GC-MS

Following extensive purification of an extract from 5000 light-grown Phaseolus coccineus seedlings by procedures including countercurrent distribution, Sephadex G10, polyvinylpyrrolidone, charcoal-celite and silicic acid partition column chromatography, TLC preparative GLC, gibberellins A₁, A₄, A₅ and A₂₀ were characterized by combined GC-MS. In addition, an unknown compound isomeric with gibberellin A₁₇ but lacking an hydroxyl group, was also detected.     

GEOTROPIC ORIENTATION IN ARTHROPODS : I. MALACOSOMA LARV?.

The geotropic orientation of caterpillars of Malacosoma americana during progression upon a surface inclined at angle α to the horizontal is such that the path makes an average angle θ upward on the plane, of a magnitude proportional to log sin α. More precisely, the product (sin α) (sin θ) is constant. This is traced to the fluctuation of the pull of the head region upon the lateral musculature of the upper side during the side to side swinging implicated in progression.     

TEMPERATURE CHARACTERISTICS FOR SPEED OF MOVEMENT OF THIOBACTERIA

The speed of translatory movement of Beggiatoa alba is governed by temperature in such a way that between 5° and 33° the temperature characteristics µ = 16,100 and µ = 8,400 respectively obtain for the temperature ranges 5° to 16.5° and 16.5° to 33°. The "break" at 16°–17° is emphasized by the occurrence of a wider latitude of variation in speed above this temperature. Above 16° the progression of Thiothrix yields µ = 8,300. The possible relation of these values to that previously obtained for similar movement in (photosynthetic) Oscillatoria is commented upon.     

PHOTIC ORIENTATION BY TWO POINT-SOURCES OF LIGHT

General formulæ are derived for the orientation of phototropic organisms in a field illuminated by two point-sources of light in the same horizontal plane. It is shown that formulæ previously found may all be derived as special cases of these general equations.     

THE GEOTROPIC CONDUCT OF YOUNG RATS

On page 263, Vol. x, No. 2, November 20, 1926, under Curve A, in the legend for Fig. 3, Ordinate scale at the left should read Ordinate scale at the right. Under Curve B, Ordinate scale at the right should read Ordinate scale at the left.