360 



MUSCINEjE. 



segments; the lower parts together with the ventral segment are employed in the 

 formation of the perigynium. The further development of the archegonia and antheridia 

 has already been described. 



In the species examined by Hofmeister the fertilised oosphere is first divided by a 

 transverse septum, /. e. at right angles to the axis of the archegonium. Only the upper 

 of the two cells, the one towards the neck of the archegonium, becomes further divided, 

 and it gives rise to four apical cells arranged as octants of a sphere, as described 

 above. 



The basal portion of the growing archegonium becomes swollen out and penetrates 

 down into the tissue of the stem, being nourished and firmly enclosed by it (the vaginula). 



As soon as the young sporogonium consists 

 of a number of cells, its wall becomes differ- 

 entiated from the inner tissue which is to 

 form the spores and elaters. In Frullania it 

 is a single circular disc of cells lying trans- 

 versely beneath the dome of the young sporo- 

 gonium from which the vertical elaters, and 

 by further divisions, the mother-cells of the 

 spores arise, a process which reminds one of 

 what occurs in Sphagnum. In most true 

 Jungermannieae there is, on the other hand, 

 a column of tissue consisting of vertical rows 

 of cells (surrounded by the wall of the sporo- 

 gonium consisting of two layers), out of which 

 the elaters and spores are formed. The elaters 

 lie, in this case, horizontally, and radiate from 

 the ideal longitudinal axis to the wall of the 

 sporogoninm (Fig. 246). In Pellia the inner 

 fertile tissue forms, after the differentiation of 

 the wall of the sporogonium, a hemisphere, 

 from the cells of which arise the spores and 

 the elaters radiating from below upwards, in a 

 similar manner to what occurs in the Mar- 

 chantieae. 

 By a rapid extension of the hitherto short seta, the calyptra is ruptured at the 

 apex, and the globular sporogonium with the already fipe spores is raised up on it. 

 Whilst the spores are ripening, the inner layer of the wall of the sporogonium becomes 

 absorbed; the single layer which still remains is ruptured at the apex, and splits into four 

 (rarely mof-e) longitudinal valves, which, flying asunder in the form of a star, carry with 

 them at the same time the elaters, by which the spores are dispersed. The elaters, when 

 mature, are long fusiform thin-walled cells, round the interior of which run from one to 

 three brown spiral bands. 



Fig. "zAd.—Jtmg 



bicuspidata ; longitudinal 



section of the unripe sporogonium s^, surrounded by tlie 

 calyptra ar ; ar' archegonia which have remained unfer- 

 tilised ; / base of the perigonium ; st stem ; b leaf : jjr points 

 to the dilated base of the seta, which still bears the hypo- 

 basal cell (after Hofmeister). 



