MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 275 



connection since he found that the rate of growth of higher plants 

 during short periods of exposure was greatest in atmospheres that 

 contained i,ooo to 2,000 parts of carbon dioxide in 100,000 and that 

 a poisonous action was exerted by an amount of carbon dioxide in 

 the atmosphere equal to 20,000 parts in 100,000. 



Notliing in the last-named investigation appears to disturb the 

 conclusion that the plant is in a tonic condition for the production of 

 flowers only when the carbon doxide of the atmosphere exerts its 

 customary pressure, and any deviation from this standard is followed 

 by an inactivity of the flower buds.^^^ 



Bonnier found that the effect of continuous electric illumination 

 upon the flowers of such plants as the tulip and hyacinth was to 

 deepen the colors and to produce closer and denser inflorescences. 

 Bafley saw that the influence of electric illumination used to supple- 

 ment daylight was to bring the opening of the flowers a week earlier 

 than in the normal, in some species, but only about four sevenths of 

 the average number of seeds was produced. In general the colors 

 of flowers were intensified in the earlier stages of blooming, and 

 sometimes an increase in the size and number of flowers could be 

 seen in such forms di^ Petunia. Rane observed that the formation of 

 flowers occurred a few days earlier in plants that had been given an 

 artificial supplementary illumination in addition to normal daylight 

 (see references on page 210), and Corbett found that some plants of 

 spinach under the influence of additional artificial illumination pro- 

 duced flower stalks, while normally grown specimens failed to show 

 any formations of this character. The most recent formal investi- 

 gation of the relation of the flower to light has been made by Beu- 

 laygue,^^'^but the principal method used in his work consisted of par- 

 tial etiolations in which flowering branches and inflorescences were 

 thrust into small dark chambers after the manner used by Sachs and 

 others, and hence his results have but a restricted value. Under the 

 conditions mentioned there was shown a lack of formation of flowers, 

 a number below the average, or a tardier appearance of the flowers 

 that were formed. Flowers etiolated in the manner indicated were 

 smaller than the normal, decoloration was more or less complete, and 

 the pedicel underwent an excessive elongation while attaining a diam- 



i^^Chapin,P. Einfluss der KohlensJiure auf das Wachstum. Flora, 91 : 348-379. 

 1902. 



i^^BeulayguC; L. Recherches phjsiologiques sur le develloppement de la fleur. 

 Montpelier. 1901. 



