26 



GENUS PALLAVICINIA 



which the archegonium itself is developed. In this terminal cell, as in 

 all Hepaticae, three nearly vertical, intersecting- walls are formed, sur- 

 rounding an axial cell. In longitudinal sections two of the peripheral 

 •cells are seen, with the axial cell between (B, C) ; in cross-section, the 

 axial cell appears triangular in shape (F). 



The young archegonium as it grows in length becomes divided into 

 two stories, by a transverse wall in each cell, and this first transverse 

 division separates the basal part, or venter, from the neck. In the three 

 peripheral cells, or more commonly in only two of them, a longitudinal 

 division is formed, so that the axial cell is surrounded by five rows of per- 

 ipheral ones. In the ventral region, other longitudinal walls are formed 

 subsequently, but in the neck region no further longitudinal divisions 

 occur, and a cross-section of the neck shows a central cell surrounded by 



A. Archegonial receptable of P. radiculosa. 



B. The same with the involucre removed. 



C. Section of the receptacle of P. Zollingeri. 



D. Section of the receptacle of P. Levieri. 



E. Section of the receptacle of P. radiculosa. 

 a. Involucre; b, perianth. 



