141 



(155) the bacteria wandered subsequently into the porouB callus tis- 

 sue''-. The cells of the algae tissues when wounded are very fre- 

 quently stimulated to cell division vii thout the formation of 

 extensive swellings. The cicatriaation tissue farmed on the 

 "leaves" of .Sargassum shows some correspondence with the 

 callus of higher plants. 



Pun^i also fom calluses, but, as it seems, less easily 

 than ^gae*. Hennings*^ observed in xylaria a ball-like callus- 

 swelling on the stroma, 



Among yasoula r Qrypto gams . various species of Selaglnella 

 may easily t"e 'tr ought to the formo-tion of callus. The cells 

 of the parenchyma, filling the passage surrounding the vascu- 

 lar sheath, are incited to abundant division by wound stimuli . 



Woody plants, especially among phanerogams, have been 

 studied often and thoroughly as to their formation of callus. 

 If cuttings of rose, poplar or willow branches of any length 

 whatever are made and Ib ft undisturbed in moist air and under 

 sufficiently high temperature, after a few days a ring-like tis- 

 sue excrescence is formed on the cambium on the cut surface* 

 This enlarges rapidly, spreads out like a roll on the out sur- 

 face and unites eventual ly 7/ ith the same kind of new formation, 

 which grows out from the pith and bark. These rools of tissue 

 have been known as callus for a long time. This is true ^i^J f * 

 their tissue construction as stated above. Sooner or later the 

 callus discontinues its growth and in mp-ny species produces ne\v 

 vegetative points, - favorable outward conditions being taken 

 for granted^ Thorough anatomic studies were made especially by 

 Trecul Cruger and Stoll^. 



^ Also in the swellings observed by Barton (On certain " 

 galls in Furoellaria and Chondrus, J. of Bot,, 1901, Vol, JJ^-^-^i 

 p, 49) a callus tissue mayfte involved, which was produced through 

 the grazing of animals and is inhabited by them. iN»B. Barton a 

 statement that Florideae starch, occurring In the "galls of 

 Purcellaria, is lacking in the normal tissues of the alga, is 

 based upon an error). 



^ Ueber Pilzabnorraitaten. Hedwlgia, 1901, Bd. XL, p. 136, 



^ Molisch 2ur Kenntn. d. Thyllen nebst Beob. Ub. Wundheil- 

 ung in d. Pfl. Sitzungsber, Akad. Wiss. Wien, 1888, B4. XCVII, 

 Abt. I, p. 264, 



* Trecul, Reproduction du bois et de I'ecorfje. Ann, Sc, 

 Hat. Bot., Serie IJI, 1853, T. XIX, p. 157. - Cruger, Einiges 

 uber die Gewebeveranderungen bei ^er Fortpflanzung duroh stecK- 

 linge, Bot. Ztg., 1860. Bd. XMII. p. 369. - Stoll, Ueb. die 

 Bildu?ig des Callus bei Stecklingen. Bot. Ztg,, 1874, Bd. XXXII, 

 p. 737. - Rechingar, Unters ub. ^. Grenzen d. Teilbarkeit im 

 Pflanzenreich, Zool, - Bot, Ges^ Wien, 1898, Bd, XLIII, p. 310. 

 Compare further the summarizing Reports by Sorauer (Handb, a. 

 Pflanzenkrankh., 2. Aufl; Bd. I, p. 561, 658) and Frank (Krankh. 

 d. Pfl, 2. Auf. 1, Bd. 1, p. 631 as also the authors named in 

 later notfces. The new work by Lockell (Die erst en Folgen a. Ver- 

 wunduhg d. Stengels dikotyler Holzgew. u. s. f. Jahresber. lo. 

 Realschule Berlin, Ost ern 1901) may boast of but little clear r 



ness. 



