2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 94 



REVIEW OF LITERATURE 



With respect to light and germination three classes of seeds have 

 been recognized for many years : ( i ) seeds germinating equally well 

 in light or darkness, (2) seeds whose germination is hindered by light, 

 and (3) seeds whose germination is favored by light. This classifica- 

 tion has emphasized the variety of the responses that may occur and 

 has proved satisfactorily descriptive for studies involving sunlight 

 or other white light. 



In 1883 Cieslar (2) reported with respect to certain seeds that 

 yellow light favored germination, whereas violet light retarded it and 

 rendered them appreciably dormant. This varying response to differ- 

 ent wave lengths of light made it evident that in sunlight or other 

 white light certain components were acting to promote germination, 

 while certain other components were acting to retard it. Upon the rela- 

 tive effectiveness of these two groups of components, either through 

 the radiant energies involved or through the particular sensitivity of 

 the seed, one might presume to depend the gross efifect of the white 

 light with respect to germination. From the more technical standpoint, 

 therefore, there were but two classes of seeds with respect to germina- 

 tion : ( I ) those whose germination was not influenced by light, and 

 (2) those whose germination was influenced by light. Seeds of the 

 latter class were designated " light-sensitive seeds," as contrasted with 

 the widely occurring seeds of the class which germinate equally well 

 in light and in darkness. The present considerations are confined to 

 light-sensitive seeds. 



Light-sensitivity as reported by Cieslar was limited for the most 

 part to small seeds without reserve food materials. In the seeds of 

 Poa nemoralis, Agrostis stolonifera, and Nicotiana nmcrophylla ger- 

 mination was reported as favored by white light, whereas the germina- 

 tion of seeds of Viscutn album was reported as hindered by white 

 light. In large measure the researches on light and germination by 

 various workers in subsequent years have been concerned with the 

 extension of these respective lists. In this respect it is to be noted 

 that sensitivity to light is now generally recognized as a widely oc- 

 curring characteristic of seeds. 



The early distinction between the efifect of " yellow " light and 

 " violet " light gained precision through subsequent researches, and 

 one finds in Molisch (9) the statement that yellow to red light pro- 

 motes germination, whereas violet, blue, or green light inhibits ger- 

 mination. This information, however, has not been widely appreciated, 

 and the more recent studies of light in relation to germination, such 



