316 RICHARD M. HOLMAN 



The range of magnifications was \ X to 2\ X but a conical 

 extension made of sheet brass, which could be substituted for 

 the lens board, so increased the distance of the lens from the 

 surface on which the image was projected that magnifications of 

 from 2\ X to 4 X could be secured when it was used. 



The tracings obtained with this apparatus made it possible to 

 follow the root curvature very satisfactorily. A piece of wire 

 thrust into the cork on which a seedling was mounted and lying 

 in the same plane as the geotropic curvature was traced each 

 time the root was drawn. The tracing of the wire and of an 

 India ink mark on the root base permitted the drawings of the 

 curving root to be brought into perfect correspondence when 

 they were superimposed. The position of the root relative to 

 gravity was recorded by tracing the image of a plumb line on 

 the first drawing of each series. 



This camera has proven its usefulness in my own work, in the 

 investigations of two other students at the Leipzig Institute on 

 twining movements and orientation of leaves and in many of 

 the exercises performed by students there, preliminary to the tak- 

 ing up of special problems. Many other uses for such a camera as 

 well as improvements in design, particularly with reference to 

 greater stability of the drawing surface, will suggest themselves 

 to those interested. 



