EXAMPLES: CYLINDRICAL OBJECTS. 371 



position || alternative ; consequently left-handed rotation. Angle 

 </> according to observations on bisected cells corresponding to the 

 inclination of the pores and (stronger) spiral stripes which latter, 

 however, vary between and about 45 ; left-handed rotation 

 confirmed. Hence, major axis of elasticity parallel to the stripes 

 the ratio of the two other axes in general unknown, though 

 in longitudinally-marked cells the radial one always the minor, 

 (b.) Thick-walled cells. Transv. sect, of the so-called primary mem- 

 brane p, of the thickened layers p or neutral, seldom t ; margin p ; 

 surface in combined effect p. The orthogonal positions neutral. 

 Hence for the primary membrane, major axis longitudinal, minor 

 radial, mean cross-tangential. The comparison of the heights of 

 the layers which produce definite colours in transverse and longi- 

 tudinal sections (marginal views) further yields the fact that the 

 two tangential axes can only differ slightly, or are possibly equal 

 (since the surface view of the primary membrane alone is not 

 observed). The elements are therefore negatively uniaxial or 

 negatively biaxial with small axial angle. For the thickened 

 layers we get from the above: major axis longitudinal, the two 

 others equal or only slightly different, judging from the feeble 

 action of the transverse section ; the elements consequently posi- 

 tively uniaxial or positively biaxial, with small axial angle. 



Cedrus libanotica Lk. (a.) Porous wood-cells with oblique pores 

 corresponding to a left-handed spiral, inclination of which to 

 the axis of the cells amounts to 45 to 80. Transv. sect, p, long, 

 sect, p, surface t, left-handed rotation. Hence, major axis of 

 elasticity in the direction of a left-handed spiral, the two others 

 unknown, (b.) Thick-walled wood-cells, with delicate left-handed 

 spiral fibres. Transv. sect. ? Margin in the outer layers neutral, in 

 the inner p ; surface p. Hence, major axis in a tangential plane, 

 the rest unknown. 



Toxics baccata L. Thick- walled wood-cells with left-handed 

 spiral fibres and similarly inclined pores; inclination to axis of 

 cells about 30 to 40. Transv. sect, p, margin p, surface t. Hence, 

 major axis in a tangential plane, the others unknown. By far 

 the greatest number of wood-cells with right-handed, left-handed, 

 steeply rising or compressed fibres, as also those with circular ones, 

 act similarly ; the pores have nevertheless about the same inclina- 

 tion corresponding to a steep left-handed spiral. 



Guntiera scabra Ruiz et Pav. Spiral vessels with right-handed 



