GROWING PLANTS UNDER GLASSES OF VARIOUS COLOURS. 61 



I put a (?) after V., as through an accident my violet glass wa& 

 broken ; but M. Deherain found that with violet he obtained a 

 less amount of carbon-dioxide than with blue. 



The above result is somewhat unexpected, so that I propose 

 repeating my experiments this summer, to thoroughly test the- 

 accuracy of this conclusion. 



Before giving the results of my experiments on the germina- 

 tion and growth of plants under different coloured glasses, it will 

 not be out of place to make a few remarks upon the general 

 effect of light on seeds. 



The question whether light is favourable to germination or 

 not was raised more than a century ago, and has never yet beer* 

 altogether satisfactorily answered. Numerous experiments have 

 been tried to solve the problem, first by Senebier in 1772', 

 latterly by Cieslar in 1884, and lastly at the Cornell Agricultural 

 College in 1889. Of the more important papers of late years, 

 those of MM. Pauchon, Adrianowski, and Cieslar may be men- 

 tioned ; yet these authors do not agree in every respect. 



In the first place it must be noted that the word " germina- 

 tion" covers two stages of growth, which are not always dis- 

 tinctly kept apart in descriptions, and what may be true for 

 one may not be equally true for the other. The first stage 

 consists of the protrusion of the radicle or the " sprouting," with 

 the consumption of reserve food materials— that is, until any 

 chlorophyll is required. Secondly, as soon as the time arrives- 

 for the plantlet to have green colouring matter, then it is obvious 

 that light is necessary. 



With regard to the first period, M. Adrianowski's * experi- 

 ments appear to be important. He found that of 200 Hemp- 

 seeds placed in diffused light and of 200 in total darkness, other 

 conditions being equal, the average number of seeds which had 

 germinated (i.e. presumably protruded their radicles) at the end 

 of one day was as 9 to 12 respectively. Similarly of Agrostis 

 stolonifera, the proportion was 5 to 54 ; of Colza, 17 to 62 ; of 

 Camclina sativa, 13 to 50. 



Using coloured glasses, he found that an average of twenty 

 series of experiments gave the proportional number of seeds 

 which had germinated at the end of a day as follows : Under 



* Archives dc V Academic Forestiere et d' Agriculture, Moscou, 6" aim. ih 

 p. 171. 



