V. MOSSES (MUSCI): SPHAGNALES—ANDRE^ALES i79 



ments is formed (Fig. 92, A). These are usually about seven 

 in number, and each of these segments undergoes regular divi- 

 sions, these beginning in the lower ones and proceeding tovi^ard 

 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 

 anticHnal wall followed by a periclinal wall in the inner of the 

 two cells (Fig. 92, E), four central cells in each segment are 

 separated from four or eight peripheral ones. The terms en- 

 dothecium and amphithecnim 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 completed, a division of the embryo into two regions becomes 

 manifest (Fig. 92, 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 appear- 

 ance and function to that of Notothylas or Anthoceros. The 

 next divisions too in the upper part of the sporogonium find 

 their nearest analogies in these forms. The central mass of 

 cells, both in position and origin, corresponds to the columella 

 in these genera, and the archesporium arises by the division of 

 the amphithecium into two layers by tangential walls, and the 

 inner of these two layers, in contact with the columella, becomes 

 at once the archesporium. By rapid cell division the upper 

 part of the sporgonium becomes globular, and is joined to the 

 foot by a narrow neck, much as in Notothylas (Fig. 93). The 

 single-layered wall of the young sporogonium becomes six or 

 seven cells thick, and the columella very massive. The one- 

 layered archesporium also divides twice by tangential walls, 

 and thus is four-layered at the time the spore mother cells sep- 

 arate. All the cells of the archesporium produce spores of the 

 ordinary tetrahedral form. The so-called "microspores" have 

 been shown conclusively to be the spores of a parasitic fungus 

 ( Nawaschin ( i ) ) . The layer of cells in immediate contact 

 with the archesporium on both inner and outer sides has more 

 chlorophyll than the neighbouring cells, and forms the 

 "spore-sac." 



