310 
RICHARD M. HOLMAN 
flattened at the border of the region of active elongation and being 
reformed at the extremity of the tip. A non-fluid medium hinders this 
progressive flattening of the tip curvature to a lesser or greater extent 
according to the compactness of the material. The diagrams (figure 6) 
of successive stages in the curvature of a root in very loose sawdust, 
Fig. 6. The tip of a root of Vicia faba at different stages in the downward 
curvature of the root in loose moist sawdust. The upper drawing is from a tracing 
of the object itself. Below is a diagram representing the same object on a larger 
scale. 
