372 POLARISATION. 



compressed threads, whose inclination to the axis > 45. Trans v. 

 sect. 2?, margin p, surface t. Consecutive position with regard to 

 the axis of the cells I;, alternative position =, consequently right- 

 handed rotation. The single spiral fibres act tolerably neutrally 

 in transv. sect. ; their major axis of elasticity is longitudinal. 

 Hence, major axis of elasticity of the vessels in the direction of 

 a compressed right-handed spiral ; the two others unknown, though 

 probably differing but slightly (judging from the action of the 

 isolated spiral fibres). 



rniderm and Cuticle. Any section t. Hence, major axis radial. 



Fibres of Muscle. According to Brlicke, and our own observa- 

 tions with muscle of Coleoptera agreeing therewith. Long- view p 

 (longitudinal), transv. sect, neutral, orthogonal positions neutral. 

 Hence, major axis of the longitudinal direction parallel, the two 

 others equal or differing but slightly ; optically positive. (The 

 opposite result of Mohl is due to an error.) 



B. Spherical Objects. 



Starch-Grains. Any sectional view t, surface neutral. Hence, 

 radial axis the major or a mean one situated nearer to the major 

 than to the minor. Possibly uniaxial and then positive. 



Inulin granules from the cells of the discs of Acetdbularia, 

 arising from their being placed in alcohol. Sectional view p t surface 

 neutral. Hence, radial axis the minor or a mean one situated 

 nearer to the minor than to the major. Possibly uniaxial and 

 then negative. 



C. Disc-like Crystals of Amylodextrine. 



The minute discs of amylodextrine have a similar structure 

 to that of sphero-crystals ; the crystal needles are not, however, 

 arranged round a centre, but radially round an axis. They are 

 distinguishable from all the above-named objects by the fact that 

 with vertical position of the axis the black cross is situated 

 diagonally, not orthogonally. The position of the effective 

 ellipses of elasticity is demonstrated by Fig. 210. In accord- 



