OF THE VEGETABLE CELL. 145 



and the Zyg^nemaceae in general, in (Edogonium and the Pal- 

 mellaceae. Here also he endeavours to show that Mohl's view 

 of the process of division is incorrect, and that it is manifested 

 in the way he describes only when Mohl's mode of experi- 

 menting is closely followed. But when very dilute solutions 

 are employed it is obvious that a delicate cellulose-septum 

 exists even in the earliest stage of the division, and which 

 was overlooked by Mohl. And further, that this delicate 

 septum, is dissolved on the addition of acetic acid when the 

 " cutaneous layer," together with the " granular layer," are 

 detached from the proper cell-wall by weak re-agents (syrup); 

 owing to which circumstance Mohl was unable to perceive 

 this septum. The author recommends a dilute solution of 

 chloride of zinc, in order to render the matter clear, from the 

 circumstance that this agent first detaches the " cutaneous 

 layer," the septum still remaining, though it is afterwards 

 also destroyed. It remained to inquire whether this delicate 

 septum were a single or a double membrane, and observations 

 on other algae {Spirogyra), as well as in Cladophora, when the 

 division was interrupted, show that this wall is double from 

 the commencement, arising from a portion of the innermost 

 cellulose-layer thrown out towards the interior. Having dis- 

 cussed the mode of division of the cell in Spirogi/ra, and the 

 Zygnemaceae in general, the author proceeds to notice the 

 process in (Edogonium and the Palmellacea^, and finds that 

 the cells of Qj^dogonium differ from those above described in 

 the circumstance that the walls of the secondary cells are not 

 applied closely to that of the parent-cell, and, consequently, 

 that a different mode of separation is manifested in this case. 

 In CEdogonium also a substance is deposited in places between 

 the parent-cell and the uppermost secondary cell, in the 

 form of a ring of cellulose. In the gelatinous AlgcB the wall 

 of the secondary cell is also not in close opposition with the 

 parent-cell, a substance being deposited between the two in 

 all parts. 



In the fourth section, the import of the " cutaneous layer," 

 as regards the cell, is shown. The subject of the author's 

 researches in this respect was afforded by (EdogoJimni, in 

 which plant the multiplication of the contents does not com- 

 mence until the elongation of the cell is completed. In this 

 case the accumulation of the plasma may be observed, and 

 the " cutaneous layer " be seen to constitute an incomplete 

 streaky lining of the cell-wall. The result of these observa- 

 tions leads to the conclusion that the cutaneous layer of the 

 plasma is the same substance as that of which the cell- wall is 

 directly formed, and that the transformation of the " cutaneous 



VOL. IV. L 



