12 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 



hypocotyls, but were not analogous to the torsions of climbing stems, 

 being produced directly by the inclined position and prosenchyma- 

 tous form of the epidermal cells. Later some important investiga- 

 tions were made by Kraus upon the water content of plants in light 

 and darkness in which he found that etiolated plants showed a 

 greater percentage of water in their composition. The exclusion of 

 light from a plant was followed by a swelling due to an increase of 

 the amount of water present, and the actual size of the plant showed 

 fluctuations during the day, which were more or less irregular. 

 The acidity of the sap of plants were observed to increase in dark- 

 ness for the most part, and in many instances the acidity of etiolated 

 plants was greater than that of normal specimens.''* 



Kraus completed some experiments upon the influence of partial 

 spectra upon plants in 1876, from which he reported that excessive 

 elongation of aerial roots and stems in Mimosa and Urtica dioica 

 occurs in red and yellow light as in darkness. Mimosa did not go 

 into a condition of darkness rigor in yellow light and soon recovered 

 from darkness rigor when placed in yellow light. This plant was 

 found to go into darkness rigor in green light in confirmation of 

 earlier results by Bert.^^ 



Batalin"'"' wrote two contributions upon this subject in 1869 and 

 187 1. His earlier work was directed toward a study of the influence 

 of light upon the separate tissues, and may be best stated in an adap- 

 tation of his own summary. Light exercises no influence upon the 

 division of epidermal cells, as illustrated by observations on Lcfidntm 

 sativum. Diffuse light facilitates division of the cortical parenchyma 

 [Le^idium sativum), and direct sunlight exercises the same effect on 

 these cells as darkness. Light acts favorably on the formation of 

 woody tissue {Cannabis sativa, Zca Mais), and the formation of 

 secondary bundles is facilitated by light ( Triticum vulgare^ Zea 

 Mais). Collenchymatous thickening is carried on only to a limited 

 extent in darkness [Solamim tuberosum), while the thickening of 

 the walls of bast and wood cells is not affected by light. Not all of 

 these results are confirmed by later investigations. 



^* Kraus. Ueber die Wasservertheilung in der Pflanze. I.Halle. 1879. III. Die 

 tagliche Schwellungsperiode der Pflanze. 1881. IV. Die Aciditat des Zellsaftes 1884. 



'5 Kraus, G. Versuche mit Pflanzen im farbigen Licht. Abdruck a. d. Sitzungs- 

 ber. d.Naturf. Ges. z. Halle. 1876. 



^^Batalin, A. Ueber die Wirkung des Lichtes auf das Gewebe einiger mono- und 

 dicotvledoner Pflanzen. Bull. d. 1. Acad. Imp. d. St. Petersbourg, 7 : 269. 1869. 



