350 



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



SvEDELius maintains that the cross-beams are given oif rather 

 regularly at nearly the same height, but this holds good only with 

 regard to the young tissue ; later on in the older tissue so many new 

 cross-beams are formed at various distance and height that their 

 distribution is quite irregular. Sometimes, but not always the cells 

 of the cross-beams in the older net are divided so that these consist 

 of a few layers of cells just as in the case of Martensia fragilis. 



Fig. 345. Martensia Pavonia J. Ag. 



Part of the thallus. 



(About 10:1). 



Finally in the older net secondary longitudinal beams are formed 

 running nearly parallel to the original longitudinal lamellæ. 

 As a rule they protrude themselves freely (cp. Figs. 345, 346), but 

 it may happen that they reach another similar cell-row and grow 

 together with it. These secondary longitudinal cell-rows were not 

 found in the material examined by Svedelius, but Svedelius 

 asserts that they are found in Martensia flagelliformis with which 

 species Martensia Pavonia therefore agrees in this respect. 



Tetrasporangia did not occur in the specimens examined by 

 Svedelius. They(Fig. 346) are formed in the oldernet, but I have also 



I 



