226 



MOVEMENT IN PLANTS, 



II. GrEOTROPISM. 



292. Geotropism of -Boot and Shoot. Grow Bean 

 seedlings in a glass-sided box ( 170). When the root 

 has produced a number of side roots, mark on the glass 

 the positions of a few of these, also of the main root. 

 Then tilt the box up at an angle of 45 and fix it in this 

 position, setting it in darkness. From day to day note 

 the change in the direction of growth of (1) the main root, 

 (2) the side roots, (3) the shoot. 



293. "Moist Chambers" for Geotropism Experi- 

 ments. Various other simple methods may be used to 

 demonstrate the fundamental facts of geotropism, using 

 seedlings. For apparatus all that is needed is a receptacle 

 in which the seedlings are given a supply of water, 

 saturated air, and aeration daily ; the apparatus should 

 be set in the dark, to eliminate the influence of light on 

 the direction of growth. 



(a) For small seeds, e.g. Wheat, place between two 

 sheets of glass a sheet of wet blotting-paper ; put the 

 seeds between paper and glass, in different positions ; put 

 additional bits of paper at the corners to prevent too great 

 pressure on the seeds, and clamp the glasses and papers 

 together with clips. When the seedlings have grown, tilt 

 the apparatus up at different angles, and note the direc- 

 tions of growth of the roots. 



(b) Pin Bean seedlings, with root .horizontal, to the 

 underside of the cork of a glass jar containing some water ; 

 or pin them to the upper side of a cork, set in a saucer of 

 water, covering all with a bell-glass. 



(c) Instead of a glass-sided box, a glass funnel may be 

 filled with moist sawdust or sphagnum and supported in 

 a bottle or jar, the seeds being planted close to the glass 

 in the funnel ; or a germination jar ( 169) may be used. 



294. Region of Geotropic Curvature in Boot. 



Take some Bean seedlings with roots about 5 cm. long, 

 and mark the root of each with transverse Indian-ink 



