150 



(167) the original causes of production are not yet known, resembles 

 many callus tissues-"" (see above). On this account I ventured 

 to mention it at this point. 



In the outer cell layers of most calliis formations a cork 

 meristem Is produced sooner or later, the products of which 

 will be termed v;ound-oork. We will return to this later. 



Orystals — isolated cr^'^stals like glands,- may often be 

 met r/ith in callus (for esKimple, in Populus, FaguB, Corylus, 

 and many others); usually, however, In lesser quantity than In 

 normal tissues, Raphides may be found (according to Sorauer) 

 In the callus of Fuohsir., According to Stoll (loc, cit.) stone- 

 cells are former" In the callus of Camellia japonioa . "gum 

 passages" in Hibiscus reglnae « I observed the formr.tion of 

 antfaocyanla . for example ^ In the callus of Populus, According 

 to Reohlnger*^ the callus of the roots of Armor acla rusti carta is 

 Bioh In starch. Vacuoles of tonic substances are very notice- 

 able In -cne oailus of many foliage trees, I found Ictex tubes 

 In the dallus of TaraiKioum roots. Differentiations moy, "fchere- 

 fore, be found in callus similar ti those which we are aectis- 

 tomed to find In the normal tissue of the plants concerned, 

 only very much more weakly developed - - oorresf)onding to the 

 character of all kataplastlo tissue, 



Massart (loc, clt.) was the first to treat the ques- 

 tion of nuclear divigion in callus tissue, which, in the 

 cases Investigated, bhly exceptionally contalred more than 

 one nucleus tt each cell. In Rlcinus, Cucurbita and 

 Tradescantia he found that, in the majority of cases, di- 

 rect nuclear division took place after injury. His suppos- 

 ition that the nuclei in all v/ound-tissiigs divide amito- 

 tically has been dispiDoved by Nathansohn , Kathansohn 

 found that only mitosis occurs in the oailus of halved 

 roots of Vicia Fab a. but mitosis as well as amitosis in 

 that of poplar cuttings. 



Conditions of callus formation 



■l a ilWlB I I llill.Mlil.;il I ■■■■plI.B ^ lfl«l ' .■■WiMriJM f ll n n^ H II ■ ■ ■■■■■■■, II 11^ ■ ■ 



It seems a matter of course that different plants should 

 bihave very differently in regard to the production of callus. 

 The time which the injured plants need to develop It, as well 

 as the amount formed in different plants fluctuates within 

 wide limits, 



The callus on young plants of Pisum develops very rapidly 

 In cotyledons of Phaseolus and Vicia, under favorable conditions, 

 it attains a considerable size even a few days after the injury. 

 In cuttings of woody plants, this formation is slower. Sorbus 

 deve'iopes abundant callus within the course of the first week; 

 Populus, Salix and many others also react relatively quickly, 

 while months elapse before cuttings fef Ostrya show a moderately 

 strong callus ring on the cut surface, 



Sorauer assumes that the "woolly stripes" are produced 

 by excess of water « 



Unters, ueb« d. Grenzen d, Teilbarkeit im Pflanzenbreich. 



Verh. Zool.w Bot, Gfes. Wien, 1894, Bd. XLIII. p. 310. 



Physiol. Unters. ueber amitotische Kemteilu 

 helm's Jahrb. f, wlss, Bot,, 1900, Bd. XXXV, p. 48. 



