A USEFUL DRAWING CAMERA 



RICHARD M. HOLM AX 

 University of California, Berkeley, Cal. 



While studying recently in the Botanical Institute in Leipzig, 

 I had occasion to follow closely the course of the geotropic reac- 

 tion and subsequent autotropic flattening of primary and sec- 

 ondary roots. To record such reactions by means of occasional 

 free hand drawings is highly unsatisfactory because of the una- 

 voidable inaccuracy of such drawings. 



The method employed by Simon (Untersuchung iiber den 

 autotropischen Ausgleich geotropischen und mechanischen Kriim- 

 mungen der Wurzeln, Jahrb. der wiss, Bot., Bd. 51, S. 81) leaves 

 much to be desired. He placed the zinc boxes with glass side 

 walls, which contained the seedlings, on their sides on the stage 

 of a dissecting microscope and by means of a camera lucida traced 

 the magnified images on paper. In this method the object is 

 subjected, during the time necessary for drawing, to a stimulus 

 acting at right angles to the direction in which it acts during the 

 intervals between drawings. If these intervals are short the 

 curvature of the root may be materially changed and a curva- 

 ture toward the side of the box will make its appearance, par- 

 ticularly if the experiment extend over considerable time. This 

 lateral curvature will occasion inconvenience and probable in- 

 accuracy in drawing the root and may bring it into contact with 

 the side wall of the box. An arrangement by which the roots 

 could be drawn without changing their position relative to gravity 

 would be more satisfactory. 



Professor Pfeffer suggested to me that a makeshift drawing 

 apparatus, consisting of a camera, once part of a now obsolete 

 photo-micrographic apparatus, the ground glass of which had 

 been replaced by a piece of clear glass and which had been em- 

 ployed by an earlier student in the laboratory, might serve my 



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THE Pi.AXT WOULD, VOL. 18, NO. II, 1915 



