174 MOSSES AND FERNS chap. 



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 w^as unable to make out clearly what the nature of 

 this branching was, but suggested a possible dichotomy. Leit- 

 geb, 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 continue the axis 

 These are apparently morphologically the same as those whose 

 growth is limited, but they continue to grow in the same man- 

 ner as the main axis. 



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, 

 yellow, or dark green, and are closely and very regularly set 

 so that the branch has the form of a small catkin (Fig. 91, A). 

 The antheridia stand singly in the axils of the leaves, and Leit- 

 geb states that their position corresponds with that of branches, 

 with which he regards them as homologous, having observed 

 in some cases a bud occupying the place of an antheridium. He 

 studied in detail their development, which differs considerably 

 from that of the other Mosses. The antheridium arises from 

 a single cell whose position corresponds to that of a lateral bud 

 on an ordinary branch. This cell grows out into a papilla and 

 becomes cut off by a transverse wall. The outer cell continues 

 to elongate without any noticeable increase in diameter, and a 

 series of segments are cut off from the terminal cell by walls 

 parallel to its base, so that the young antheridium consists of 

 simply a row of cells, comparable to the very young anther- 

 idium of the Marchantiaceae. Intercalary transverse divisions 

 may also arise, and later some or all of the cells, except the ter- 

 minal one, divide by longitudinal walls, usually two intersect- 

 ing ones in each cell, so that the antheridium rudiment at this 



