AN HISTOLOGICAL STUDY OF REGENERATIVE PHE- 

 NOMENA IN PLANTS 1 



CORA MAUTZ BEALS 



Instructor of Botany, Principia College 



Introduction 



Nemec ('05), Pfeffer ('05), and Prantl (74) employ the word 

 regeneration in its narrowest sense when they consider that it is 

 the formation of new parts exactly alike in number and position 

 to the organs injured or removed. Since new structures gener- 

 ally originate only from actively growing tissues, regeneration is 

 practically limited to the embryonic tissues of the root and shoot. 

 For example, if an old root tip is removed, the new root tip is 

 regenerated. Roots forming on the stem, however, are not 

 regenerated roots but simply adventitious roots. An example 

 of this type is the root developed at the nodes of Tradescantia 

 when that plant is placed in a glass of water. The extreme 

 opposite of this view has been held by Vochting (78), Goebel 

 ('02), Morgan ('01), and Klebs ('03) who consider the develop- 

 ment of dormant buds present on the part before injury to be a 

 regeneration phenomenon. They, therefore, include in their 

 definition of regeneration a phase of normal vegetative growth 

 which might be termed merely the stimulation of bud develop- 

 ment, the production of new roots or new buds, etc., in any 

 position in which these, organs do not normally occur. A more 

 moderate view, however, is assumed by Miss Kupfer ('07) who 

 says that regeneration "ought to be limited to organs formed 'de 

 novo' at a place or under conditions not normally so [formed]. 

 Therefore, she excludes latent root and shoot development which 

 occur, for example, when a willow twig is placed in the ground, 

 and as would be included in the definition by Goebel ('02), 

 Vochting (78), and Morgan ('01). 



1 An investigation carried out at the Missouri Botanical Garden in the Graduate 

 Laboratory of the Henry Shaw School of Botany of Washington University and sub- 

 mitted as a thesis in partial fulfillment of the requirements for the degree of master 

 of arts in the Henry Shaw School of Botany of Washington University. 



(369) 



77 



Ann. Mo. Bot. Gard., Vol. 10, 1923 



