1024 RECORD OF CURRENT RESEARCHES RELATING TO 



Cell-division in Conferva and CEdogonium.* — N. Wille has 

 observed the mode of cell-division in a large newly discovered variety 

 of Conferva amoena which he calls var. norvegica. The cell-wall 

 appears to be composed of pointed H-shaped pieces, a smaller and a 

 larger one always alternating, the latter enclosing the margins of the 

 former like the lid of a box. The whole row is surrounded without 

 and within by a dense substance which binds it together. The 

 division of the cells is preceded by the formation of a watery layer, 

 which may be termed the " lengthening-layer," in the interior of the 

 dense layer which lies on the inner side of the cell. The further 

 development of this lengthening-layer causes the older pieces of cell- 

 wall to become separated from one another. At this period the 

 nucleus divides, becoming first of all constricted in the middle, and 

 then breaking up into two parts, which at once begin to separate from 

 one another, jiarietal protoplasm at the same time collecting between 

 them. The new septum then develops from the lengthening-layer 

 in the form of a circular ridge inside the cell, the central part being 

 perhaps formed at the time, and divides it into two halves. When 

 fully developed cells open, the cell-wall breaks up into H-shaped 

 sharp-pointed pieces ; but when cells open while in the act of division, 

 the ends of these pieces are united by a membrane, since in this case 

 the line of dissociation does not pass through the innermost denser 

 layer. 



Conferva flaccosa, Ag. (3 Norm Semlice can multiply by the cells 

 losing their connection with one another. 



Cell-division in CEdogonium is thus described by the same writer. 

 The ring of cellulose is here the " lengthening-layer," and is formed in 

 the same way as the corresponding layer in Conferva ; but its subse- 

 quent development differs in the greater firmness of the cell-wall. In 

 occasional abnormal instances the development resembles that in Con- 

 ferva. While, in Conferva, the lengthening layer and the septum are 

 closely united with one another, in CEdogonium they are quite distinct. 

 In the latter the septum is fonned simultaneously in a disk of parietal 

 protoplasm, which is no doubt produced by the activity of the nucleus, 

 this latter appearing to divide like that of Conferva. The ring of 

 cellulose expands to a new piece of cell-wall, by which means the 

 young septum is raised up by the pressure in the lower daughter- 

 cell, uniting them in its growth with the wall of the mother-cell. 



Incrusted Filaments of Conferva. f — Professor Hanstein has ob- 

 served, in a ditch at Godesberg, which receives the very warm water 

 of a steam engine, as well as water impregnated with iron, conferva- 

 filaments enclosed in a thicker or thinner, continuous or interrupted, 

 ochre-coloured envelope. The filaments were stift" bristles or knotty 

 moniliform threads. The interrupted envelopes Hanstein believes to 

 have been originally continuous, but to have been ruptured and separ- 

 ated by subsequent extension of the filaments. Both the girdles and 



* ' Christiania Vidensk. Forliandl.,' 1880. See ' Bot. Ceutralbl.,' i. (1880) 

 p. 579. 



t 'SB. niederrhein. Ges. Bonn,' v. (1878), p. 78. See ' Hedwigia,' xix. 

 (1880) p. 118. 



