HEP A TICM. 



301 



The sporogonium also originates in different ways. The fertilised oosphere 

 is always first divided in the archegonium into two cells, the upper of which, 

 facing the neck, forms the growing apical cell; but this divides in very different 

 ways in the different groups: — in Anthoceros by oblique walls inclined in four 

 directions ; in the IMarchantiese and Ricciese by walls inclined alternately in two 

 directions ; while the sporogonium of the Jungermanniese contains, even in its very 

 earliest stage, four apical cells lying beside one another like octants of a sphere, 



FlC. 215.— Later stage in the development of the archegonia and origin of the sporogonium of Marchantza poly- 

 morpha; /,//, young archegonia ; III, II', after absorption of the axial row of cells of the neck ; ^' when ready for fer- 

 tilisation ; K/ -/'/// the cells of the mouth of the neck a- relaxed after fertilisation; the fertilised oosphere y shows its 

 first divisions. In these figures si is the lowest cell of the axial row in the neck which is last converted into mucilage; e in 

 I-IVl\\e central cell, in A' the unfertilised oosphere ; // in V-VII the perianth in process of development ; /^ the 

 unripe sporogonium in the ventral portion of the archegonium which has developed into the calyptra ; a neck of the 

 archegonium ; f wall of the sporogonium ; st its stalk ; inside the sporogonium are the young elaters arranged in rays, 

 among them the spores. (/-F///X300, IX about 30.) 



which divide simultaneously by horizontal septa. When the young sporogonium 

 has in this manner attained its destined height, and partially even at an earlier 

 period, a number of divisions of different kinds take place in the segments of the 

 apical cell, by which the structure is completed. The wall of the sporogonium 

 also becomes differentiated from the tissue from which the mother-cells of the 

 spores are to arise ; if elaters are formed they originate from the same tissue, the 

 cells ceasing to divide transversely at an earlier period and remaining long, while 



