o 



40 Dansk Botanisk Arkiv. Bd. 3, Nr. 1. 



two rows ; now and then one of these branches get indefinite growth 

 contributing in this way to the ramification of the plant. 



The main stem increases by means of an apical cell from which 

 flat segments are cut off gradually: from these the branches grow 

 out, even before the segments are divided. The branches in my plant 

 issue mostly from every sixth segment, and it is only in a very few 

 and rare cases that the space between the branches may be either 

 shorter or longer than the above mentioned. Falkenberg found, in 

 his Mediterranean plant, about four segments between the branches. 

 The segments are first divided into two cells, one large and one small, 

 and in such a way that the first wall is formed underneath the inser- 

 tion of the branch; the next wall, dividing the large cell, is formed 

 opposite to it, the segment by these divisions being divided into three 

 cells, a larger cell in the middle and two smaller peripheral ones 

 on both sides. Then finally the cell in the middle is divided by two 

 walls in a central and two opposite peripheral cells. It is a well 

 known fact that this plant has previously been included among the 

 Rhodomelaceæ*), but the above-described way of cell-division is 

 quite in concord with that found in the Delesseriaceæ and differing 

 from that in the Rhodomelaceæ. Compare in this connection the 

 schematic figures of both kinds of division given by Falkenberg, 

 1. c, p. 4. The main stem in the upward growing branches is terete 

 like that of the prostrate main axis. The branches carry mostly 3 — 4 

 branchlets ; but now and then in more weakly developed plants the 

 erect branches are reduced to a single branchlet. 



The final shape of the branchlets is flat. 



The lowest segments of the branchlets remain terete; but in 

 the following segments the two opposite peripheral cells become 

 divided in such a way that first a smaller cell is cut off in the upper 

 peripheric corner by a convex wall and then a similar cell is cut 

 off in the corner below (cp. Fig. 337 b). No further divisions do 

 take place. This division of the cells is quite in agreement with that 

 found in other Delesseriaceæ. 



The branchlets are not ramified until a side-branch is formed 

 at rather definite distance from their base (about 15 segments). 



The apical cell of this one gets the same or nearly the same 

 strength and the same direction as that of the mother-axis. Both 



Compare Falkenberg, I.e., p. 708. 



