134 MOSSES AND FERNS CHAP. 



As the archegonium approaches maturity the cover cells 

 become very much distended and project strongly above the 

 surrounding cells. In stained microtome sections their walls 

 colour very strongly, showing that they have become partially 

 mucilaginous. This causes them to separate readily, and they 

 are finally thrown off, so that in the open archegonium no trace 

 of them is to be seen. The walls of the canal cells and the 

 central cell undergo the same mucilaginous change, but here it 

 is complete, and before the archegonium opens the partition 

 walls of the canal cells completely disappear, and the neck con- 

 tains a row of isolated granular masses corresponding in num- 

 ber to the canal cells. The ventral canal cell is quite as large 

 as the egg, which consequently does not nearly fill the cavity at 

 the base of the open archegonium (Fig. 66, D) after the canal 

 cells have been expelled. The egg did not, in any sections 

 studied, show clearly a definite receptive spot, but appeared to 

 consist of uniformly granular cytoplasm with a nucleus of 

 moderate size. The upper neck cells in the open archegonium 

 become a good deal distended, and the canal leading to the 

 egg is unusually wide. Surrounding the central cavity the 

 cells are arranged in a pretty definite layer. 



Miss Lyon ((2), p. 288) states that she has frequently 

 found archegonia in A. Icevis, produced upon the ventral side 

 of the thallus. 



The Sporophyte 



Hofmeister was the first to study the development of the 

 embryo in Anthoceros, and described and figured correctly the 

 first divisions, but his account of the apical growth, which he 

 supposed was due to a single apical cell, and the differentiation 

 of the archesporium, was shown by the careful investigation of 

 Leitgeb ((7)., v.) to be erroneous. The following account 

 is based upon a large series of preparations of A. Pearsoni and 

 A. fusiformis, which seem to agree in all respects. After 

 fecundation the egg at once develops a cellulose wall and be- 

 gins to grow until it completely fills the centre cavity of the 

 archegonium. As it grows the uniformly granular appear- 

 ance of the cytoplasm disappears, and large vacuoles a're 

 formed, so that the whole cell appears much more transparent. 

 The granular cytoplasm is now mainly aggregated about the 

 nucleus, which has also increased in size (Fig. 66, E). The 



