VI MOSSES {MUSCl): SPHAGNACE.£—ANI)RE/EACEA£ 165 



Later there may be a further division, so that the cortex of the 

 main axes frequently is four-layered. While the cells of the 

 young cortex are small, and the tissue compact, later there is 

 an enormous increase in size of the cells, which finally lose 

 their protoplasmic contents and resemble closely the hyaline 

 cells of the leaves. Like the latter, the cortical cells are 

 perfectly colourless, and usually have similar circular perfora- 

 tions in their walls. The resemblance is still more marked in 

 vS. cynibifolimn, where there are spiral thickened bands, quite 

 like those of the hyaline leaf cells. On the smaller branches 

 the cortical cells ^ have been found to be of two kinds — the 

 ordinary form and curious retort-shaped cells with smooth 

 walls and a single terminal pore. 



TJie Branches 



Leitgeb '■'' has studied carefully the branching of Sphagnum, 

 which corresponds closely to the other Mosses investigated. 

 The branch arises from the lower of the two cells into which 

 the outer of the two primary cells of the segment is divided. 

 In this cell, which ordinarily constitutes part of the cortex, walls 

 are formed in such a way that an apical cell of the ordinary 

 form is produced. These lateral branches themselves branch 

 at a very early period, and form tufts of secondary ones. 

 Schimper was unable to make out clearly what the nature 

 of this branching was, but suggested a possible dichotomy. 

 Leitgeb, however, concludes that it is monopodial, and that 

 each branch corresponds to a leaf, as do the primary branches. 

 The growth of all the lateral branches, both the descending 

 flagellate ones and the short upright ones at the top of the 

 stem, is limited, and lasts through one vegetative period only. 

 This, however, is not true of the branches that are destined to 

 contain the axis. These are apparently morphologically the 

 same as those whose growth is limited, but they continue to 

 grow in the same manner as the main axis. 



t> 



The Sexual Organs 



The sexual organs in Sphagnum are produced on branches 

 that do not differ essentially from the sterile ones. The leaves 

 of the antheridial branches are usually brightly coloured, — ^red, 



^ Schimper ( i ), p. 39. - Leitgeb ( i ). 



