INTRODUCTION TO CRYPTOGAMIC BOTANY. 463 



of a peduncule. In general one arcliegoniuni only is impreg- 

 nated, and then the abortive archegonia are scattered over the 

 vaginula, or borne on the walls of the calyptra. The sporan- 

 gium itself is usually more or less elliptic, with the sides occa- 

 sionally grooved or compressed. It is almost always borne on 

 a peduncle of greater or less length, which may be sunk in the 

 receptacle, X)r otherwise. In some cases, as in Sphagnum, the 

 apparent peduncle is the elongated stem. The sporangium 

 itself consists of a central cylindrical or more or less deeply 

 winged columella, with which the spores are in contact ; and 

 a wall immediately confining the spores, which is in most cases 

 attached by filaments to the outer wall. In Sphagnum, how- 

 ever, the spore-sac and outer wall are confluent. In a few 

 Phasca alone the columella is absent or imperfect. The spore- 

 bag is usually called the sporangium, and the whole fruit, the 

 theca ; but if the fruit in JungermMnnice be a sporangium, 

 that in mosses is perfectly homologous. The sporangium has 

 often a swelling at the base, which is called an apophysis. It 

 opens above by a definite circular fissure, so as to throw off a 

 little lid or operculum, which often remains attached to the 

 inside of the calyptra, and sometimes, as in Wardia, to the 

 columella. In a very few cases only there is no separation. 

 At the point of separation there is often a deciduous ring. 

 The separation of the lid may at once expose the spores; they 

 may, however, be covered with a membrane, entire or toothed 

 at the circumference ; or there may be one or two rows of teeth 

 surrounding the aperture, which are not fewer in number than 

 four, and if more, some multiple of that number. 



510. The teeth arise from the thickening of the cell-walls of 

 two contiguous cells, and if there is a second row of teeth the 

 next two cell-walls towards the centre are thickened. In some 

 cases, as in Barbula (Fig. 98, a), two or more distinct eleva- 

 tions are formed, instead of a uniform thickening, and if one or 

 three elevations be formed instead of two, the normal number 

 of teeth is disturbed. The outer row of teeth arises frequently 

 from the innermost layer of cells of the outer wall, the inner 

 from the outermost layer of the spore-sac ; but this is not 

 positively constant, and where the peristome is double, 



