334 MOSSES AND FERNS chap. 



pear-shaped (Fig. 167, B), and a periclinal wall is then formed 

 in the apical cell. The cells of the stalk undergo no longi- 

 tudinal divisions, and it remains permanently composed of 

 three rows. 



Klindig ^ first called attention to the real state of affairs, 

 and since, C. Miiller '^ has investigated the matter further. The 

 central tetrahedral cell of the young sporangium (archesporium) 

 has cut off from it, by periclinal walls, the primary tapetal cells 

 (/), and in the meantime the wall of the capsule forms repeated 

 radial divisions but no periclinal ones, and, unlike that of the 

 eusporangiate Ferns, alvv^ays remains single-layered. A surface 

 view of the sporangium at this stage shows the last -formed 

 lateral segment to still retain its triangular form, and the cell 

 divisions in it are very regular. After two or three transverse 

 divisions, a median vertical wall follows, and in each of the 

 resulting cells a transverse wall. Of the two upper cells, one, 

 according to Miiller,^ remains undivided, the other divides again 

 by a vertical wall, and the inner of the two cells thus formed 

 by further transverse divisions forms the stomium or mouth of 

 the sporangium. 



The cells of the young sporangium contain but little 

 granular contents, and the divisions are very evident. As soon 

 as the archesporium is formed its contents begin to assume a 

 more granular appearance, and become more highly refractive 

 than those of the surrounding cells. The contrast between the 

 archesporial cells and those of the wall increases as the sporan- 

 gium grows older. 



The first division in the central cell begins soon after the 

 separation of the primary tapetal cells. Th.e direction of this 

 first wall is usually transverse, but may be more or less 

 inclined, or even vertical. In each of these cells a wall is 

 formed at right angles to the first-formed, and the quadrant 

 cells are again divided into equal octants. Each of these eight 

 cells divides once more (Fig. 167, G), and the sixteen spore 

 mother cells, found in most Ferns, are complete. In Onoclea 

 strutJiioptei'is I found twelve as the ordinary number, but at what 

 point the division is suppressed was not made out. During the 

 division of the central cells the tapetal cells also divide, first 

 by radial walls only, but later by one set of periclinal walls. 

 This doubling of the tapetum, while it occurs in the majority 

 1 Kundig(i). - Miiller, C. (2). ^ Miiller, I.e. 



