(8) CHAPTER I, 6 



RESTITUTIOK 



Living plants or plant organs are often stimulated to pro- 

 cesses of growth and to the formation of certain kinds of new 

 structures by the violent removal of some already existing part. 

 If this leads to the rebuilding or transformation of organs, 

 different results are conceivable. 



1, The newly formed portions arise on the place of amputa- 

 tion and resemble the lost portion in all essential points. If 

 for example, the tip of a root is removed a new root tip will be 

 formed at the p3)aoe of injury. Decapitated shoots often v^avelop 

 callus on the surface of the cut and from this numerous adventi- 

 tious shoots; many marine algae proliferate abundantly on the 

 cut surface; other similar examples might be cited. 



2. The newly formed portions resemble in all essential 

 points those lost; they are not produced, however, at the place 

 of injury, but at a greater or lesser distance from it. If, for 

 example, we remove from a root not only the tip but also older 

 portions further back, no regeneration takes place as in 1. On 

 the contrary, the cut root is incited to the formation of lat- 

 eral roots which arise above the place of amputation. 



3, The newly formed parts arise on the surface of the cut, 

 but do not resemble the lost parts (heteromorphosis) . Oases of 

 this kind arise when, for example, root cuttings of Taraxacum 

 develop leafy shoots on the apical surface of the injury, i. e. 

 on the one toward the root apex, or when seedlings of Bryopsis 

 form rhizoids instead of lost "sprouting parts". 



4. The newly formed portions neither resemble those lost 

 nor are they produced on the surface of amputation. Sachs found 

 in the case of Cucurbita that after the removal of all shoot buds, 

 the root buds, pres^^nt in each leaf axil, developed into knot- 

 like structures, vbchting-'- recently described his observations 



on certain species of Brassica, where, after the removal of the 

 vegetative points from all sprouts, he found leaf-cushions trans- 



(9) forming in the same way. It should be noticed that the newly 

 formed portions arise from organs already existing, at least in 

 their incipiency. 



The processes of regeneration result in a reproduction of 

 the original forms, or structures similar to them can be created, 

 only in the cases named under 1, in which the new parts are pro- 

 duced at the place of injury and resemble those lost in all es- 

 sential points. Various modifications are still conceivable, 

 however, either the surface of the injury in its entirety takes 

 part in the regeneration, or only portions of it; further, at 

 the place of injury, there arise either one ner form alone or 

 several of equal value, near one another. Adventitious shoots 

 of leafy plants, as well as the proliferation of the thallophy- 

 tes, capable of regeneration, in this process pass first through 

 a stage similar to the "juvenile -forms"; the former with simpl6 

 leaves, the latter with a cord-like thallus base. 



A complete agreement of the lost with the newly formed or- 

 gan, a restitution ad integrum , will be attained only when the 

 following conditions are fulfilled ;- 



•*■ ySchting, Zur experimentellen Anatomic. Wachr. k, Ges. 

 Wiss. Gottingen, 1902. Heft 5, 



