lyo MOSSES AND FERNS chap. 



The Sporogonium 



Waldner ^ has recently studied carefully the development 

 of the embryo of SpJiagnum, which differs essentially from all 

 the other Mosses, and has its nearest affinity in the Antho- 

 ceroteae. In the species ^. acutifolium, mainly studied by 

 Waldner, the sexual organs are usually mature in the late 

 autumn and winter, and fertilisation occurs early in the spring. 

 The ripe sexual organs are found in a perfectly normal condi- 

 tion in mid-winter, under the snow, and apparently remain in 

 this condition until the first warm days, when they open and 

 fertilisation is effected. The first embryos were found late in 

 February, and development proceeded from that time. 



The first division in the embryo is horizontal and divides it 

 into two cells. In the lower of these the divisions are irregular, 

 but in the upper one the cell walls are arranged with much regu- 

 larity. The upper cell is the apical cell of the young embryo, 

 and from it, by walls parallel to the base, a series of segments is 

 formed (Fig. 8o, A). These are usually about seven in number, 

 and each of these segments undergoes regular divisions, these 

 beginning in the lower ones and proceeding towards the apical 

 cell, which finally ceases to form basal segments and itself 

 divides in much the same way as the segments. The latter 

 first divide by two vertical divisions into quadrants, and in each 

 quadrant either directly by periclinal walls, or by an anticlinal 

 wall followed by a periclinal wall in the inner of the tv/o cells 

 (Fig. 80, E), four central cells in each segment are separated 

 from four or eight peripheral ones. The terms endotheciuni 

 and ainpJiitJiecium have been given respectively to these two 

 primary parts of the young Moss-sporogonium. By the time 

 that the separation of endothecium and amphithecium is com- 

 pleted, a division of the embryo into two regions becomes 

 manifest (Fig. 80, C). Only the three upper segments, in- 

 cluding the apical one, give rise to spores ; the lower segments 

 together with the original basal cell of the embryo form the 

 foot, which in Sphagnum is very large. The cells of the foot 

 enlarge rapidly and form a bulbous body very similar in 

 appearance and function to that of Notothylas or Anthoceros. 

 The next divisions too in the upper part of the sporogonium 



1 Waldner (2). 



