10 



Ktore examples may be given for these cases than for those 

 in which, as after plasmolysis, a new formation of the cell- 

 wall takes place after injury to the cells and after violent 

 removal of pieces of cell-wall, with which is connected a aim- 

 ultaneous loss of living cell substance. 



In the first place there should be mentioned here also, 

 the much investigated Siphoneae-*-, which in part, can heal their 

 wounds even in a very short time by a newr formation of cell- 

 wall. All Siphoneae which have been tested, (Anadyonene, Bo- 

 trydium, Bryopsis, Caulerpa, Codium, Derbesia, Halimeda, TTdotea, 

 Valonia, Vaucheria) are capable , 7/ithout exception, of re^atoring 

 the cell-wall. The Phycomycetds, which resemble the Siphoneae 

 and which, in forming soar membranes are also protected by the 

 narrow liimen width of their mycelial tubes, act also like the 

 Syphoneae^, 



So far as is known, in almost all cases, the Injured cells 

 of higher plants lack the ability of restitution. It isf Imma- 

 terial whether the results of the protoplasmic loss play the 

 chief role, whether the contact of the exposed protoplasm with 

 the external environments acts as a distributing factor, or 

 whether other factors turn the scales:- in any case, the in- 

 jured cells almost always break down without having healed their 

 cell-walls. As yet only a few exceptions are known. 



If the upper part of the nettle hair of Urttca dioioca is 

 broken off, it is immatBrial whether only the tip or a larger 

 part be lost - the protoplast now and then forms a delicate 

 scar membrane at a varying distance from the surface of the 

 break. In one case on a mutilated hair, I found a new, very 

 delicate walled tip, not absolutely regular, (Compare figure 1), 



Perhaps even regeneration of the tip becomes possible un- 

 der suitable conditions, so that the same nettle hair may again 

 (13) become effective %s a weapon. ^ Moreover Kallen^ has already an- 

 nounced, that the hairs of Urtica urens can close their wounds 

 with membranes. It is very possible that the nettle-hair cells 

 of Urtica can also be incited to the formation of membrane 

 caps by means of plasmolysis. 



■^ Of the abundant lijjerature. the following may be named: 

 Hanstein, Ueb, d, Lebensfahigkeit der Vaucheria-ielle. Sitz. 

 Ber. d, Hiederrhein, Ges, Bonn, 1872; Hanstein, Eeproduktion 

 und Reduktion von Vaucheria-Zellen. ^anstein's Botan. 5bhandl., 

 1880, Bd. IV, p. 45; Schmitz, Beob". ub, d. vielkemigen Zellen 

 d. Siphonocladiaceen. =Pestchr. d. naturforsch. Ges. Halle 1879, 

 p. 275; Noll. Ueb, den Einfluss der Lage auf d.„Morphol, Aus- 

 bildung einiger Siphoneen. Arb. d. Bot. Inat. Wurzburg, 1888^ 

 Bd^ III, p, 466; Wakker, Die Keubildungen an abgeschnittenen 

 Blattern von Caulerpa prolifera. Kon, Akad. Wetensch. Amsterdam, 

 Bd, III, 2. p. 251; KJ^emm, Ueber Caulerpa prolifera. Flora 1893, 

 Bd. LXZVII, p. 460; Kuster, Ueber Vernarbungs-und Proliferations-^ 

 erschein, bei Meeresalgen. Flora, 1899, Bd. LXXZVI, p. 143; 

 Winkler, Ueber Pol^ritat, Regeneration und Heteromorphose bei 

 Bryopsis, Pringsheim's Jahrb. f. wissenschaftliche Bot. 1900 

 Bd, XXXV, p, 449; Prowazek, Beitr, z, Protoplasmaphysiologie. 

 Biol. Cbl., 1901, Bd, XXI, p. 87. 



^ Compare especially Van Tieghem, Mouv. rech. s. 1. Mucor- 

 ineens, Ann. So, Nat. Bot., 4, ser., Tom, 1, 1875, p. 19. 



'^ Das Verhalten d, Protopl, in d. §ew. v. Urtica urens 

 entwicklungsgeschichtlich dargestellt. Flora, 1882, BS. LXV, 

 p. 65. 



