8o MOSSES AND FERNS chap. 



of tv/o cells, of which the upper one forms the base of the 

 antheridium body (Fig. 31, D). At this stage and the one 

 preceding it Sphcerocarpus recalls very forcibly the structure of 

 the antheridium of the Characese, although the succession of 

 walls is not exactly the same. The divisions of the central 

 cells are extremely regular, walls being formed at right angles, 

 so that the sperm cells are almost perfectly cubical, and the 

 limits of the primary central cells are recognisable for a long 

 time. 



The development of the antheridial envelope begins much 

 earlier than that about the archegonium, but in exactly the 

 same way. By the time that the wall of the antheridium is 

 formed the envelope has already grown up above its summit, 

 and as the antheridium develops it extends far beyond it like 

 a flask, at the bottom of which the antheridium is placed, and 

 through whose neck the spermatozoids escape. These are 

 very much like those of the other Hepaticae, and in size exceed 

 those of most of the Marchantiacese, but are smaller than is 

 usual among the Jungermanniaceae. 



Leitgeb ^ studied the germination of the spores, which 

 remain united in tetrads permanently. He found that all the 

 spores of a tetrad were capable of normal development, which 

 does' not differ from that of Riccia or other thallose Liverworts. 

 A more or less conspicuous germ tube is found at the end of 

 which the young plant develops, one of the octants of the 

 original terminal group of cells becoming, apparently, the 

 apical cell for the young plant. The latter rapidly grows in 

 breadth and soon assumes all the characters of the older plant. 

 Leitgeb (Fig. 17, PI. IX.) shows a condition that looks as if at 

 an earlier stage a two-sided apical cell had been present, but 

 he says nothing in regard to this. The sexual organs appear 

 while the plant is extremely small. Leitgeb says he observed 

 the first indications of them on individuals only one millimetre 

 in diameter, and before the first papillate hair on the ventral 

 surface had been formed. 



Corresponding closely in the origin and structure of the 

 sexual organs to SphcErocarpiis, but differing much in habit, is 

 the peculiar genus Riella, containing seven species, all sub- 

 mersed aquatics, and, so far as is yet known, confined to 

 Northern Africa and Southern Europe. The plant (Fig. 32, 

 1 Leitgeb (7), vol. iv. PI. IX. Fig. 17. 



