282 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 



competition of concurrent organs and furnished with a supply of food- 

 material, although in such instances the customary morphological 

 differentiations do not ensue. 



Sachs' researches were so extensive and included so many of 

 the phases of the suhject that it will be profitable to take up at this 

 point only those which attempted an explanation of the nature, or the 

 cause of the etiolative phenomena, and as his point of view naturally 

 changed considerably in the thirty years in which he had this subject 

 under consideration it will be necessary to touch only upon the 

 conclusions he was disposed to consider as final (pp. 7-11). The ab- 

 normal form of etiolated leaves was regarded as due to pathological 

 conditions, as the result of some investigations carried on by Prantl 

 (p. 13, 1873) in Sachs' laboratory, and the reduced size of many 

 plants including seedlings grown in darkness was attributed directly 

 to lack of nutritive material, although he distinctly disclaimed ap- 

 proval of Kraus' self-nutriiion theory as he found that leaves on por- 

 tions of shoots confined in dark chambers in partial etiolations attained 

 considerable size. The unusual elongation of stems was determined 

 by him to be due to the increased size of the cells rather than to a 

 multiplication of these elements, and to take place in the absence of 

 the paratonic or retarding influence, which he supposed was exerted 

 on growth by light. An important feature of Sachs' explanation of 

 the phenomena of etiolation was that specific formative material was 

 necessary for the construction of the various organs, particularly 

 flowers. Flowers could be developed only when the buds were laid 

 down and supplied with anthogenic material which was a product of 

 leaves in sunlight, and might not be replaced with building material 

 from storage organs. He anticipated in a suggestive way the 

 "adaptive theory" of . etiolation when he described the stems of 

 climbing plants as " naturally etiolated," and thus incapable of any 

 further effort to reach sunlight by excessive elongation. Lastly he 

 believed to have demonstrated that the action of the ultra-violet rays 

 of the spectrum were necessary for the formation of the special antho- 

 genic or flower-forming substances, and that these rays exerted an 

 important influence upon the growth and development of plants. Of 

 these several contentions it is to be said that the extended endurance 

 of etiolated leaves, and of other organs to confinement in darkness, and 

 the fact that fully etiolated members are capable of taking up normal 

 development when brought into normal illumination lead to the con- 



