584 



SCIENCE. 



[N. S. Vol. XVII. No. 432. 



SCIENTIFIC BOOKS. 

 The Influence of Light and Darkness upon 

 Groiuth and Development. By Daniel 

 Trembly MacDougal, Ph.D. Published by 

 the aid of the David Lydig fund bequeathed 

 by Charles P. Daly. Memoirs of the New 

 Tork Botanical Garden, Volume II. New 

 York, 1903. (Issued January 20, 1903.) 

 Large 8vo. Pp. xiv + 319. 

 This notable contribution opens with a 

 short historical account (34 pages) of investi- 

 gations bearing upon the subject under con- 

 sideration, the earliest of which was that of 

 John Eay in 1686, followed in 1727 by Hales, 

 in 1754 by Bonnet, in 1776 by Mees, in 1782 

 by Senebier, and in 1783 by Tessier. This 

 brings the record down to the opening of the 

 nineteenth century, in which we find seven- 

 teen names in the first half, among which are 

 DeSaussure (1804), DeCandolle (1806), Davy 

 (1815), Knight (1841), Payer (1842) and 

 Draper (1844). Shortly after the middle of 

 the century Sachs began his work (1859), 

 and continuing for thirty years or more, 

 added 'an enormous number of facts con- 

 cerning growth and the relations of light to 

 plants,' and ' led the way to nearly all of the 

 modern work upon this subject.' No doubt 

 he revolutionized this part of the science of 

 plant physiology, and yet it is a curious fact, 

 as Dr. MacDougal remarks, that ' scarcely a 

 single one of his conclusions concerning etio- 

 lation and the influence of light upon growth 

 is tenable at the present time except in 

 modified form.' Stimulated by the work of 

 Sachs, a host of investigators sprang up, their 

 number increasing rapidly during the closing 

 quarter of the century. The latest names 

 recorded are those of Eicome and Noll (both 

 in 1902), immediately preceded by Livingston, 

 Goff, Wiesner, Nabowick, Neljubow and 

 Schulz (all in 1901). 



The body of the book (166 pages) is made 

 up of careful records of observations upon 

 ninety-seven different species of spermato- 

 phytes and pteridophytes. Here, as one reads 

 page after page of observations, it is made 

 very plain that this portion of the book re- 

 quired a deal of patient work. By means of 

 drawings made from photographs the text is 



helped out and made much plainer than would 

 have been possible otherwise. The earlier 

 work was done by the use of small portable 

 dark-chambers of zinc or wood, but after the 

 removal of the author to the New York 

 Botanical Gardens in 1899 a specially con- 

 structed room in the middle of the museum 

 building was used. Here the temperature 

 was very constant, and a normal atmosphere 

 was secured by proper ventilating apparatus. 

 Entrance to the room was through double 

 doors with a vestibule between, and the plants 

 under observation were examined by means 

 of a single-candle or a four-candle power 

 electric lamp. 



As a matter of course, the most obvious 

 result of the growth of plants in total dark- 

 ness, aside from the loss of green color, is the 

 more or less complete suppression of the leaf- 

 blades and an elongation of the internodes 

 of the stems. There are also marked changes, 

 which, however, are not readily seen, in the 

 minute anatomy of the leaf and stem, as are 

 well shown by many excellent figures. In 

 some cases the histological changes are quite 

 remarkable, as in the leaf of Oxalis lasiandra, 

 the stems of Qalium cvrccezans and a seedling 

 oak. The epidermis of Opuntia opuntia 

 shows very striking differences, as is the case 

 to a less degree in most plants observed. 

 Here, however, while the epidermal cells are 

 usually much modified, the stomata themselves 

 are but little changed on the etiolated leaves. 

 Among the interesting modifications figured, 

 none are more so than those of the 'pitcher 

 leaves ' of species of Sarracenia. 



In a discussion of the effect upon the plant 

 of prolonged or continuous light, the author 

 concludes that " increase in the total duration 

 of illumination to which a plant is exposed, 

 during its vegetative period, either by artifi- 

 cial nocturnal illumination, or by cultivation 

 in Arctic regions, results simply in a corre- 

 spondent acceleration of the seasonal develop- 

 ment of the plant, by which a greater amount 

 of work is accomplished within a given num- 

 ber of days. The extinction of the daily 

 ' resting period ' brings no distinct reaction 

 so far as important anatomical features are 

 concerned, although an exaggerated produe- 



