46 GENERAL DIFFERENTIATION OF THE PLANT-BODY 



other cases, for example, in detached leaves of many plants l , the formation 

 of roots takes place but not the formation of shoots. I have obtained 

 the formation of roots even upon the severed inflorescences of Klugia 

 Notoniana and other Gesneraceae, which possessed no vegetative organs 

 but only some small bract-leaves ; a further development of these has 

 however not yet taken place 2 . 



The propagative capacity of the different organs is very slight in 

 some groups. In the ferns, for example, no case is known in which new 

 plants have been formed from leaves detached from the parent, excepting 

 in the case of the ' stipules ' of Marattiaceae, in aposporous ferns and 

 other abnormal instances, although shoots very often appear in this 

 group upon the leaves which are still in connexion with the parent. In 

 the Lycopodieae adventitious shoots are only known upon the first leaves 

 of the embryo-plant of Lycopodium inundatum, the later leaves do not 

 seem to be able to produce them. 



The behaviour of the roots in the Pteridophyta is likewise variable. In 

 some of them a formation of shoots takes place upon the uninjured roots 3 , 

 and such roots are, even when they are detached, specially suited for 

 regeneration. The behaviour of Ophioglossum is interesting 4 : A forma- 

 tion of shoots often takes place on the roots of uninjured plants very 

 near their apices, and always upon very few roots of one plant, but if 

 the apex of the plant be destroyed 5 then formation of shoots is much more 

 copious, and particularly so from any severed root-tip a few centimetres 

 long ; the formation of shoots therefore takes place not at the shoot-pole 

 but at the root-pole itself where evidently normal ' shoot-forming material ' 

 arises, but this material in the uninjured plant flows to the shoot itself. 

 Any other portion of the root is also capable of regeneration. 



It is interesting to note that the behaviour in regeneration of detached 

 leaves is not in all circumstances the same. Sachs was the first to 

 direct attention to this in the case of Begonia 6 . The adventitious shoots 

 which arise upon leaves taken from plants which have arrived at their 

 flowering period very soon produce flowers, but if the leaves be detached 

 from plants which are not yet ripe for flowering then their adventitious 



1 Many plants also form ' leaf-cuttings ' without external influence. In this way adventitious shoots 

 arise on the base of the fallen leaves of species of the aroid genus Zamioculcas and on the detached 

 lower leaves of Nasturtium lacustre. 



2 This has now (1898) taken place in Tydaea hybrida; the inflorescences treated as cuttings have 

 grown out into tubers. 



3 See Part II of this book. 



1 Poirault, Recherches anatomiques sur les cryptogames vasculaires, in Ann. d. Sc. Nat. ser. 7, 

 xviii. p. 148. 



5 Similar relationships of correlation are known elsewhere, for example, in Populus tremula; 

 many adventitious shoots are formed on the roots of felled trees of this species. 



6 Sachs, Physiologische Notizen i, in Flora, 1892. 



