15 



« 



Diaphyses of this kind were thoroughly described for Mar- 

 chantia and Lunularia by Kny-'-. Since my experiments have proved 

 that any desired number of compensatory structures may be called 

 forth by cutting back the rhizoids, this development of the par- 

 enchjTOia cells x)n the trichome base may be brought into undoubted 

 connection with the wound stimulus or its results. To conclude 

 from Kny^s data, other factors also seem able to excite a stimu- 

 lus, similar to the one usually associated with the nutilation 

 of the rhizoid. At least Kny states that diaphyses occur also in 

 rhizoids in which the membrane is intact. Then the secondary 

 hairs find gt the tip of the primary ones an energetic opposition 

 to further elongation, which may lead to a bending and curling. 

 (18) Kny observed further that even a tertiary hair may develop in a 

 secondary fi'ig. 3b) and that, occasionally, two cells at the 

 base of the primary rhizoid, instead of one, may develop into 

 compensatory hairs. 



In the case of many multicellular algae, the thallus of 

 which is made up of filaments consisting of rows of simple cells , 

 (for example, Trentepohlia ) similar regeneration phenomena take 

 place after the removal of the growing tip. The uppermost cell, 

 left intact, continues the growth of the mutilated filament. 

 Therefore, the regenerating phenomena of growth proceeds here also 

 from one cell*^. 



In the case of the higher plants, restitution processes of 

 this, the simplest .kind, are rare. The processes of healing and 

 regeneration observed by Miehe on Tradescantia virginica are some- 

 • wh5t comparable to the diaphyses of Marchantia rhizoids. After 

 the dying off of single epidermal cells, or small cell groups, 

 the wound is closed over by the growth of the intact np:ighboring 

 cells.- In this way, one may occasionally find single cells com- 

 pletely filling out the gap of the dead neighboring elements. I 

 will return later to theSe phenbmena. (Chapter IV, 4). 



Regeneration of tissues, brought about by unlimited division 

 of the exposed cells, often takes place Xn thallnphytes in so far 

 as a differentiation of pith and bark tissue may be recognized 

 in them. 



In the sclerotia <)f Coprinus stercOrarius , investigated by 

 Brefel^, the outer coat consrists of kix to eight layers, with 

 black -put icularized walls'. If these are removed, the inner cells 

 regenerate a new outer coat. "Some division in the inner cells, 

 as well as the very close association of the cells which have di- 

 vided td produce the thinner tissue -of the outer coat together 

 with a stretching of the •utermost c^ll-layers to form the great 

 cells of this coat are the processes, which must necessarily 

 $ake place, In order to develop the outer coat from the inner 

 cells^. This experiment miiy be repeated with sclerotia, as long 

 as the inner substance lasts. 



Algae, especially the Florideae, behave similarly in the ex- 

 tent to which they exhibit tissue with distinguishable pith and 

 bark. By truncations and tears, or after removal of the bark, a 



■^ Eigentuml, Durchwachsungen an den Wurzelhaaren zweier 

 Marohantiaceen. Verb. Bot. Ver, Prov. Brandenburg, 1880, Bd. 

 X2JJ, p. 2. 



^ Illustrations in de Wildeman: Sur la reparation chez 

 ' quelques algues. Mem, cour, et autres mem. acad. Belgique , 

 1899, T. LVIII. 



^ Brefeld, Botanisoh© Untersuch. uber Schimmelpilze . 1837, 

 Bd. Ill, p, 25. 



