MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 281 



signed to the lack of formation of carbon compounds, and to an in- 

 creased retention of water. The last statement is, of course, fairl}^ 

 correct so far as our present knowledge of the subject bears upon 

 the matter, but the other portions of his explanation do not need 

 further attention. A few years later (1811), Ellis''"^ made an examina- 

 tion of the facts presented by Senebier, and without the addition of 

 any further observations questioned the conclusions of the latter as 

 to the alterations in color and the lack of chlorophyl in plants grown 

 in darkness, and advanced the supposition that the abnormally large 

 amount of carbon dioxide in etiolated leaves would destroy the green 

 color and, " Hence, therefore, the etiolated state of plants depends 

 on a deficiency of alkaline, or a superabundance of acid matter, by 

 which the usual operation of the alkali is reduced or counteracted ; but 

 the sun's rays, by withdrawing and decomposing this excess of acid, 

 enables the alkali to resume its former action, and thereby restore 

 the green colour of the leaf." No actual contribution to the subject 

 was made until the time of Sachs (1859-1892), and Kraus (1869). 

 The latter attributed the excessive elongation of stems to the abnor- 

 mally high tensions of the parenchymatous tissues, the cells of which 

 not only increased in length far beyond the normal limits, but also 

 showed an increase in number, thus stretching the ductile stems be- 

 yond the normal limits. The failure of the leaves to attain normal di- 

 mensions was accounted for by the supposition that these organs were 

 capable of growth only by means of material constructed locally by 

 their own activity and hence, were incapable of development in dark- 

 ness (see pp. II and 12). It is to be said that the excessive elongation 

 of stems in darkness is accompanied by either an exaggerated growth, 

 or multiplication of the cells of parenchymatous tissues, or by both, 

 and that the excessive increase in length or thickness of stems in 

 darkness is due in part to the action of these tissues, although other 

 tracts are active as well. The alterations in form are, as a matter of 

 fact, due to the correlated action of the entire body of the shoot and 

 may not be ascribed to any one set of cells. It has been demon- 

 strated by Jost, Sachs and myself that leaves may carry on de- 

 velopment in such manner as to be able to attain a stature ap- 

 proximately normal as to extension and size when relieved of the 



13^ Ellis, D. Farther inquiries into the changes induced in atmospheric air by the 

 germination of seeds, the vegetation of plants and the respiration of animals, p. 132. 

 181 1. Edinburgh. 



