THE PLANT WORLD 71 



The Influence of Light and Darkness upon Growth and Develop- 

 ment, '^y Daniel Trembly MacDougal. (Memoirs of the New York 

 Botanical Garden. Vol. II, p. 1-319 ; fig. 1-176. January 20, 1903.) 



Occasionally there appear in this country the published results of 

 some botanical investigation which, because of the thoroughness and 

 care with which it has been prepared, causes every American botanist 

 to rejoice at the renewed evidence of the high place his chosen science is 

 taking at home and the constantly increasing recognition accorded it 

 abroad. Such a publication has recently appeared, written by Dr. D. T. 

 MacDougal, Director of the Laboratories of the New York Botanical 

 Garden, and it is to be hoped that aside from its scientific value, the 

 work may also serve as an example of what a finished piece of research 

 of this kind should be. 



After an exceptionally full and complete resum^ of all the important 

 literature upon the subject, thus giving the necessary historical basis for 

 the succeeding parts, detailed observations are given upon nearly one 

 hundred species of plants which have been cultivated for a considerable 

 time in various degrees of darkness and light. Instead of all of these 

 species being closely related and propagated in practically the same 

 manner, as has been the practice of former investigators along this line. 

 Dr. MacDougal experimented with plants representing numerous habitats, 

 from the aquatics to spiny xerophytes, and these were grown from bulbs, 

 cuttings, seeds and by every other method that was possible. As might 

 be expected from such a wide range of types and conditions, the general 

 considerations deduced from the observations are numerous and quite 

 conclusive. A mere enumeration of them can give no idea of the vast 

 amount of interesting and valuable information set forth. The effect of 

 darkness and the consequent etiolation upon the growth and develop- 

 ment of the tissues, organs and members of climbing plants, aquatics, 

 succulents, woody perennials, etc., is shown in the greatest detail and 

 there is also much that is new and important relating to various storage 

 organs and their ability to serve the plant when its normal methods of 

 forming organic food are prevented. 



The various theories as to the nature of etiolation are briefly summed 

 up and it is shown that no single explanation previously set forth is suffi- 

 cient to account for all the conditions which are produced by absolute 

 darkness. The fundamental principle is established that in all species 

 there is the greatest difference between the morphological differentiation 

 in the tissues of etiolated and non-etiolated plants. That this differentia- 

 tion is unquestionably due to the action of light upon the plant at the 

 proper time is abundantly shown, thus offering a fine demonstration of 

 the fact that growth and development are independent and easily separable 



