SECOND GROUP. MUSCINEAE. 



all other Mosses, inasmuch as its embryo has not a two-sided apical cell, but is divided 

 by anticlinal walls which are transverse to the longitudinal axis, and these are few in 

 number. The oospore divides first by a wall at right angles to the axis of the 

 archegonium into a lower and an upper cell ; the lower cell undergoes only a few more 

 divisions, the upper developes into the sporogonium ; a number of transverse walls 

 with corresponding longitudinal walls are first formed, and this is followed by inter- 

 calary growth. The rest of the Mosses which have been examined on this point have, 

 as was said, a different arrangement of the cells in the embryo. After one or more 

 transverse walls have made their appearance in the oospore, an oblique wall is formed 

 in the uppermost cell and then another in the opposite direction, and in this way a 



two-sided apical cell is produced which gives 

 off a number of segments. These segments 

 are disposed as transverse disks (Figs. 131, 

 132). The transverse section of a young 

 embryo shows therefore two cells with the 

 form of half cylinders, separated by the 

 segment- wall ss. Then a second wall ap- 

 pears at right angles to s s, so that there are 

 now four quadrants of a cylinder (Fig. 131, 

 B\ but these are not formed in Archidium. 

 Next an anticlinal wall is formed in each 

 quadrant, and to each a periclinal is added 

 (Fig. 131, B}. There are now the following 

 cells to be seen in the transverse section of 

 the embryo ; four inner cells forming a figure 

 which approximates to a square and eight 

 outer peripheral cells. The archesporium 

 and the columella proceed from the former in 

 the Bryineae and Phascaceae, and the wall 

 from the latter. The square of cells, the 

 fundamental square, may be called the endo- 

 thecium^ the peripheral cells the amphithecium. 

 It is obvious that the separation into amphi- 

 thecium and endothecium might have been 

 effected in a more simple manner, namely by the appearance of a periclinal line in each 

 quadrant, which would have separated four inner cells forming the endothecium from 

 four outer, the amphithecium (Fig. 131, C); and this in fact does happen in Funaria 

 hygromelrica and Ephemerum, and we see once more by this case how little weight is 

 to be attached to the succession of cell-divisions ; the same result can be obtained by 

 more than one sequence of cell-divisions, and it is the result that we are concerned 

 with more than with the process. A periclinal wall, arising in each quadrant in the 

 endothecium, separates an outer cell-layer, the archesporium (Fig. 131, D, the shaded 

 part), from the central part, the columella, which suffers further division and becomes 

 a mass of cells, while the archesporium becomes itself the spore-producing tissue 

 without further change, or divides and forms a mass of spore-mother-cells. The 

 amphithecium undergoes other periclinal and radial divisions before the archesporium 



FIG. 131. 'A embryo of Ceratoaon purpureus in optical 

 longitudinal section. B, C, D transverse sections through 

 the capsular portion of young sporogonia, B and C of 

 Ceratodon purpureus, D of Funaria hygrometrica ; Q the 

 fundamental square, s primary wall of the embryo. After 

 Kienitz-Gerloff, JB, C, D diagrammatic ally represented. 



