MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 213 



It will be necessary to make a critical examination of the results 

 of the observations described in the present memoir in order to deter- 

 mine how far the separate factors enumerated above are to be con- 

 sidered as responsible for the forms and activities of etiolated plants, 

 and in order to test the validity of the various theories that have been 

 proposed in explanation of the relations of plants to light and darkness. 



The manifestations to be considered include among other features 

 alterations in the seasonal or periodic activity coupled with altera- 

 tions in the duration or length of existence of the various members 

 of the shoot. These departures from the normal mode of existence 

 serve as a means of analysis of the economic value of the reserve 

 supplies in seeds and other storage organs. It follows naturally that 

 the form and general aspect of the shoot are greatly altered by a 

 development in which the usual relation to light is disturbed, and 

 that such divergences are accompanied by unusual methods of dif- 

 ferentiation of tissues, which are developed in a manner markedly 

 different from the normal, some being suppressed, others accentuated, 

 and in some instances new tissues arising. Variations occur in the 

 form, size, and number of the elements, the structure and character 

 of the walls being materially different from the normal, while the 

 protoplasts diverge chiefly in the character of the inclusions, and 

 composition of the vacuolar fluids. Organs and members may be 

 suppressed, or undergo a development of mass beyond the normal in 

 a manner wholly determined by the general physiological relations 

 of the species in question. The abnomalities may go even deeper and 

 include variations in the dorsiventral organization of the plant, neces- 

 sarily accompanied by alterations .in the character of the reflexes 

 exhibited ; many of the more important forms of irritability being sup- 

 pressed. The non-development of the various stimulative reactions 

 is purely a loss of functional capacity in some instances, while in 

 others the change from the normal is still more sweeping and 

 embraces the non-formation of the tissues in which the power of 

 reaction is ordinarily invested. The relations of light and darkness 

 to reproductive organs and their products are so complex that an 

 interpretation of the behavior of these mechanisms may be made only 

 after a consideration of the mode of formation of the reproductive 

 bodies, and of the method of their dissemination, as well as of the 

 general features of the nutrition of the plantlet arising or developing' 

 from such bodies. 



