184 MOSSES AND FERNS CHAP. 



The Sexual Organs 



The species of Andreaa may be either monoecious or dioe- 

 cious. Archegonia and antheridia occur on separate branches, 

 but their origin and arrangement are identical. The first- 

 formed antheridium develops directly from the apical cell of the 

 shoot, and the next older ones from its last-formed segments, 

 but beyond this no regularity can be made out. In the first one 

 the apical cell projects, and its outer part is separated from the 

 pointed inner part by a transverse wall. This is followed by a 

 second wall parallel to the first, so that the antheridium rudi- 

 ment is composed of three cells. Of these the lower one takes 

 little part in the future development. Of the two upper cells 

 the terminal one becomes the body of the antheridium, the other 

 the stalk. In the former, by two inclined walls, a two-sided 

 apical cell is developed, and the subsequent growth is the same 

 as in the Bryales. The middle cell of the antheridium rudi- 

 ment divides repeatedly by alternating transverse and longi- 

 tudinal walls, and forms the long two-rowed stalk of the mature 

 antheridium. On comparing the antheridium with that of the 

 other Mosses, we find that it approaches Sphagnum in the long 

 stalk, but in its origin and the growth of the antheridium itself, 

 it resembles closely the higher Mosses. 



The first archegonium also is derived immediately from the 

 apical cell of the female branch, and the first divisions are the 

 same as in the first antheridium. Here, too, the subsequent 

 development corresponds exactly with that of the higher 

 Mosses, and will be passed over. The ripe archegonium shows 

 no noteworthy peculiarities, and closely resembles in all respects 

 that of the other Mosses. 



The Sporophyte 



The more recent researches of Waldner (2) on the develop- 

 ment of the sporogonium of Andrecca have shown clearly that 

 in this respect also the latter stands between the Sphagnacese 

 and the Bryales. The first division in the fertilised ovum is 

 transverse and divides it into two nearly equal parts. The 

 lower of these divides irregularly and much more slowly than 

 the upper one. In the latter (Fig. 95, E), the first division 

 wall is inclined, and is followed by a second one which meets 

 it nearly at right angles, and by walls inclined alternately right 



