MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 35 



known that illumination is indispensable to germination of some 

 species, and that darkness is equall}^ necessary for others. In both 

 instances the stimulating effect is probably concerned, although the 

 action of the heat rays is not eliminated. 



The foregoing resume may be held to include notices of nearly 

 all of the more important researches bearing upon the subject of this 

 paper. Doubtless some worthy of notice have escaped the au^^hor's 

 attention, and still a few others will be referred to in the discussion 

 in the closing section of this memoir. 



SCOPE, PURPOSE AND METHODS OF THE PRESENT 



OBSERVATIONS. 



In the earlier investigations of the author ^'^ upon the growth of 

 plants in darkness, and in atmospheres lacking carbon dioxide, con- 

 clusions of value concerning the relation of development to nutrition, 

 and as to the regulatory action of the plant in darkness were reached. 

 It was found, however, that a satisfactory explanation of the phe- 

 nomena of etiolation might not be made from any such limited series 

 of experiments, and that current generalizations as to the relation of 

 light to growth and reactions of plants in darkness rested upon simi- 

 larly isolated series of observations in which only a few species of 

 plants were used, and under conditions not always under full control. 

 It was therefore planned to carry out a large number of etiolations 

 upon species selected to represent types of the most diverse morpho- 

 logical and physiological character and habit. In the seven years 

 during which the work has been in progress ninety-seven species 

 have been cultivated in continuous darkness with control plants in 

 ordinary alternation of da3dight and night. Aquatics, creepers, 

 climbers, succulents, mycorhizal forms, geophilous and aerial shoots, 

 mesophytes and spiny xerophytes, were grown from tubers, corms, 

 rhizomes, cuttings of leaves and stems, seeds and spores. 



By the extension of the observations over such an extended 

 period, it was also possible to obtain much interesting and valuable 

 information as to the inertia, or capacity for endurance of species 

 with storage organs under conditions not suitable for the acquisition 

 of formation of complex organic food, a subject hitherto but little 

 touched. 



1^6 MacDougal. Relation of Gi-ovvth of Leaves to the Chlorophyl Function. Jour. 

 Linn. Soc. London, i : 526. 1S96. 



