118 HOFMEISTER, ON 



the individual air-cavities from one another, have also 

 multiplied considerably. A remarkable transverse ex- 

 pansion has preceded the repeated bipartitions (PL XVI, 

 fig. 17, at the bottom, on the left side); the sides of the 

 cells are at an early period forced above the air-cavity, to 

 which they are contiguous. The process of the production 

 of those cells of the epidermis of the receptacle, which are 

 in connexion with the cellular layers separating the air- 

 cavities, consequently soon helps to form the lid of those 

 cavities, which at an earlier stage was represented only by 

 the young stomate or its mother-cell. 



The base of the side walls of the air-cavities of Mar- 

 chantia soon produce moniliform chains of cells filled with 

 chlorophyll. In Rebouillia most of the cells of those walls 

 do not usually do more than project considerably, but 

 individual cells grow out into short, cellular rows. The 

 walls of the air-cavities of the receptacle of Fegatella remain 

 for a very long time smooth and even. 



The median component part of the fructifying shoot of 

 Targionia J/ypqpJiylla does not become changed into a 

 specially formed receptacle, but developes the archegonia at 

 once, the latter being from one to five in number (PI. XV, 

 fig. 21). The lower half of the archegonia is pressed into 

 the exceedingly narrow fissure, within which the lateral 

 wings of the fore edge of the fertile shoot confine the rudi- 

 mentary median part. The necks of the archegonia, which 

 are bent upwards, project from the fissure into space. A 

 considerable increase of the parts of the tissue adjoining 

 the archegonia in front commences even during the longi- 

 tudinal growth of the latter. At the junction of the 

 median shoot with the lateral wings of the fore edge, 

 above the point of attachment of the archegonia, the cellu- 

 lar layers expand and multiply vigorously in a longitu- 

 dinal direction ; their thickness is proportionate to the 

 development of the layer of air-cavities. Before the apices 

 of the archegonia open, a flat covering is formed, which 

 exceeds the archegonia in height, and which unites the 

 approximated lateral portions of the fore edge into one 

 surface. The separation of the upper side of the stem into 

 the layer of air-cavities and the epidermal layer takes 



