128 pringsheim's r*esearches on chlorophyll. 



VII. Results in detail of some Experiments. 



For the production of the coloured lights employed in 

 these experiments the following solutions were used : 



For red . . . iodine in bisulphide of carbon. 



,, yellow . . . potassium bichromate. 



„ green . . . copper chloride. 



„ blue . . . ammonia copper sulphate. 



Their spectra are described on pages 87 and 88, and 

 are represented in fig. 28. 



Successive experiments in each group followed one another 

 immediately, sufficient time — usually only five to ten minutes 

 — being allowed for adjustment of the apparatus and object. 

 In order to facilitate recognition of the cells, especially in 

 experiments where no effect is visible, the bending of the 

 object in a V-shaped manner into a long and short leg is use- 

 ful. Where as in experiments 21 and 22, slight effect is 

 observed from light in an atmosphere of hydrogen, it is due 

 either to the long exposure of the cells permitting the develop- 

 ment of much heat, and is therefore a thermal effect, or it 

 may be that the hydrogen has not completely expelled all 

 the oxygen from the gas chamber — not having been intro- 

 duced sufficiently long before commencement of the experi- 

 ment. It should begin to pass through the chamber about half 

 an hour before insolation. It is further to be noted that hair- 

 cells of Tradescantia and coloured cells which are not green 

 are with difficulty destroyed in light ; after eighteen to twenty 

 minutes in feebly-intense coloured light they remain intact. 

 It must be also remembered that aerial parts do not respire 

 freely under water, and can only take up to a small degree 

 oxygen dissolved in water. They are, in fact, almost in the 

 conditions of an oxygen free chamber. It is, therefore, 

 more^. difficult to kill them under such conditions by light, 

 i.e. they require longer exposure than do green cells of water- 

 plants. Such long duration of exposure may, however, 

 induce heat-effect, and it is therefore well to lay carefully 

 the object so that only one side of the cells is submerged, 

 the other side being exposed to the atmosphere. 



The details regarding the experiments arranged in the 

 following tables sufficiently explain themselves : 



