61 



In«-ot,her cases grov/th-arresting factors are involved, es- 

 pecially any kind of disturbances ih nutrition by which a local 

 growth in thickness of the cell merabrane is caused. 



Klebs-L observed in various algae very active thickening in 

 the restitution membrane of plasmolysed cells fOoropare above 

 p. 14). Either a uniformly thickened and distinctly striated 



(63) membrane is formed all around the contracting protoplasts, or 

 the cellulose is deposited In excess at certain places. Here 

 and there knobbed and oone-lrlke protuberances are formed, which 

 project into the lumen. But it is Impossible to observe that 

 the specific differentiation of the plant cellf? here influenced 

 the shape of the net? cellulose formations, T'teTe sften appear 

 in cells of the same kind, elliptical or conlrjaX masses of cel- 

 lulosg, or masses deposited regularly on all sides of the 

 cells . We observed the same thing In distixrbances of nutri- 



■ tion, or under the influence of factors arresting growth in the 

 roothairs, rhizoids (compare fig, IS), pollen tubes, Siphoneae, 

 and other algae. Large oellulbse masses are produced sometimes 

 sphero-crystalloid in form, sometimes delicately "coralloid" 

 cones,, or small branched beams, which traverse the lumen of the 

 cell diagonally (IJoll), but layers thickened with bordered 

 pits are never found among them. 



Heavy wall thickenings resembling collenchjmia occur, ac- 

 cording to Wortmann^, in the epicotyl, epidermis and bark of 

 PhafeeoluS and other plants, if they are forcibly hindered in 

 carrjring out their reaction curvatures. The thickenings occur 

 on that side of the axis in which the cells have prepared for 

 the reaction curvatures by an abundant accumulation of proto- 

 plasm. 



According to the statements of several authors, heavy 

 wall thickenings appear in the fundamental tissue, as in the 



(64) vascular bundles of plants cultivated in nutrient soliitions of 



Beitr. z. Phys. d, Pflanzenzelle , Tubinger tJnters., 

 M. II, Heft 3 (1888), p. 489. 



„ * Compare Schaarschmidt, Zellhautverdickungen u. Cellulin- 

 korner bei Vaucherien and Charen, Bot. Cbl,, 1885, Bd. XXII, 

 p. 1. Further statements are to be found, for instance in 

 Stahl, Ueb. den Ruhezustand der Vaucheria geminata* Botan. Zeitg. , 

 1879, Bi. XXXVXI, p. 129; Heinricher, Z. Kenntn. d. Algengattung 

 Sphaeroplea, Ber. d. D. Bot. Ges., 1883, Bd. I, p. 433; Noll, 

 Experim. Unters. ttb, d. Wachstum d, Zellmembran. Abhandl. Senck- 

 enberg. Haturf. Ges., 1883, Bd. XV, p. 101, Zacharias, Ueb. Ent- 

 sleh, u. Wachstum d. Zellhaut. Ber. D. D. Bot. Ges., 1888, Bd. 

 VJ, p, LXIII. Haberlandt, Eeb. Einkapselung d. Protopl. m. 

 Rucksicht auf d. Punkt. d. Zellkerns. Sitzungsber. Akad^ Wiss. 

 Wien, 1889, Bd. XCVIII Abt. 1, p. 190. Tomaschek, Ueb, d. Ver- 

 di ckungsschicht en an kunstl. hertjorgeruf , Pollenschlauchen v. 

 Colohicum autumn. Botan. Cbl., 1889, Bd. XXXIX, p, 1. Raciborski, 

 Ueb. d. Einfl. Suss, Bedingungen auf die Wachstumsweise des Bas- 

 idiobolus ranarum. Flora, 1896, Bd. LXXXII, p. 113* Sokolowa, 

 Ueb, d. Wachstum d. Wurzelh. u. Rhizoiden. Bull. Soo. Imp. Nat. 

 Moscou, 1897, p. 167, Llimmerraavr, Ueb. eigentumlich ausgebil- 

 dete innere Vorsprungsbildurtgen in d. Rhizoiden v. Marchantieen. 

 Oesterr. Bot. Ztschr., 1898, Bd. L, p. 321 and many others. 



^ Zur Kenntnis der Reizbewegungen. :^otan, Ztg, 1887, Bd, 

 XXXXV, p, 785, Elving; Zur Kenntn, d. Krummungsercheinungen d, 

 Pfl. Ofversight Finska Vet. Soc, Fotrh, 1888, Bd. XXX. 



