90 SUMMAKY OF CUERENT RESEAECHES RELATING TO 



elements which were derived from the plate arrange themselves into a 

 thread, which elonsates and has a serpentine form. 



When the daughter-nucleus divides, these processes are repeated, 

 but the elements of the plate of the daughter-nucleus often differ in 

 form from those of the parent-nucleus. When cell-division follows 

 division of the nucleus, this takes place precisely in the way described 

 by Strasburger. 



Superficial Growth of the Cell-wall.* — F. Schmitz adduces 

 fuither evidence in supjiort of his previously published view "f" that 

 the increase not only in thickness, but also in superficies of the cell- 

 wall, is due not to intussusception, but to apposition. The arguments 

 are drawn chiefly from the structure of the cell-wall in Zijgnema, 

 Spirogyra, Ulothrix, and other filamentous algte, in which the outer 

 surface of the cell-wall exhibits very fine markings or even puncta- 

 tions due to very minute pores. If the cell-wall was constantly being 

 stretched by intussuscejition, this marking would continually increase 

 in scale, which, ho\vever, is not the case. On the contrary, the rupture 

 of the outermost passively stretched layer is a very common pheno- 

 menon with algse and other plants, a fact which is in complete 

 accordance with the theory of apposition, while it is difficult to 

 explain on that of intussuscei)tion. 



Mechanism of the Structure of the Cell-wall.^ — F. v. Hohnel has 

 carefully examined the behaviour, under various conditions, of the 

 cell-walls of bast-fibres and other elements in the structure of vegetable 

 tissues. From the facts observed, he draws a conclusion adverse to 

 the theory that the cell-wall consists of crystalline micellae. The 

 chief and efiicient cause of the optical pro2:)erties of the cell-wall he 

 considers to be molecular tensions, which, however, occur only between 

 the thinnest layers of the walk The occurrence of these tensions can, 

 he states, be absolutely proved ; and experiments on fine threads of 

 other substances are sufficient to show that they are competent to 

 produce the phenomena of polarization. The same facts will also 

 account for many j)eculiarities of the phenomena of swelling which 

 have not hitherto been explained. 



Function of Lime in Germination. § — Experiments by previous 

 observers on PhaseoJus multiflorus had led to the conclusion that lime 

 has no function in connection with the transport of starch in germi- 

 nating seeds ; but that it is connected with the transformation of reserve 

 into formative materials, as, for example, of starch into cellulose. A 

 fresh series of experiments by A. von Liebenberg tends to show that 

 plants may be divided into several groups in respect to the presence 

 or absence of lime, and to its function in their germinating seeds, 

 viz. : — 



1. Lime is absolutely necessary when the reserve-materials are being 



* SB. Versammlung deutsclier Naturf. u. Aerzte in Eisenach, Sept. 19, 18S2. 

 See Bot. Centralbl., xii. (1882) p, 108. 



t See this Journal, i. (1881) p. 908. 



+ Bot. Ztg.. xl. (1882) pp. 595-GOG, 616-25. 



§ SB. Akad. Wiss. Wien, Ixxxiv. (1882) p. 405. See Naturforschcr, xv. (18S2) 

 p. 419. 



