SOME NEW MEMOIRS. 



On the Photographic Analysis of Plant Movements. By Dewevre and 

 E. Bordage. Revue generak de Botanique, February 15, 1892. 



Photography has already been applied with so much success to the 

 study of animal locomotion, that MM. Dewevre and Bordage have 

 lately been adopting this method for determining the movements of 

 plants. To the top of the part to be studied, a minute thread of 

 blackened glass, ending in a bright head, is attached by a drop of glue. 

 The movement of the bright head is recorded on a sensitised plate 

 contained in a photographic camera. By means of two cameras 

 placed one above, and the other by the side of, the plant, a record of 

 the movement'in a horizontal and a vertical plane is obtained at the 

 same time. The plant may be placed in a blackened box, and the 

 tubes of the cameras inserted in holes in the sides, while the glass head 

 is illuminated by light entering at a small hole in one side ; but as 

 continued darkness is often disadvantageous and sometimes not 

 allowable from the nature of the experiment, the authors find it 

 sufficient if the mouths of the cameras are directed towards inter- 

 nally-blackened tubes, placed beyond the part the movement of 

 which is to be registered. 



Experimenting with the Convolvulus, they have been able to 

 certify that this climber exhibits true heliotropism, a fact denied by 

 several authors, though Darwin thought it existed, but in a very 

 slight degree. 



They have also studied the action of light of different colours on 

 the heliotropic movement, e.g., in the case of Lepidium sativum, which 

 is not a climber, they found yellow light to have no action. The 

 curvature of the stem in response to illumination began in the green, 

 increased towards the blue and violet, and reached a maximum at 

 the limit of the violet and ultra-violet. It then slowly decreased in 

 the ultra-violet region, but was still feebly manifested even in that 

 part of the spectrum where silver-salts cease to be blackened and 

 fluorescent substances to shine, and only stopped entirely a little 

 further on, at a distance equal to twice the length of the luminous 

 band obtained with a quartz prism. 



An attempt was also made to analyse the normal movements of 

 circumnutation described by a root pushing through the soil. As 

 the presence of an indicator, however small, attached to the sensitive 

 tip of a root causes a Darwinian curvature in the opposite direction, 

 another method had to be employed. The whole root was covered 

 with a thin layer of lamp-black, except the tip, at the level of the 

 region of growth. This part remaining white, affected the sensitive 

 plate, provided sufficient light was received. By this arrangement 

 it was determined that the root, thus left quite at liberty, described 

 a very regular circumnutatory movement, with less oscillation than 

 the tip of the stem. 



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