THE HIGHER CRYPTOGAMIA. 191 



protoplasmic covering of the cell-wall. These granules are 

 usually very few in number ; sometimes however they are 

 more abundant, and they are not unfrequently furnished 

 with a thin coating of chlorophyll. 



The necks of the archegonia when perfect frequently 

 exhibit a central string of cells in their longitudinal axis 

 (PL XXV, figs. 3, 5, 6). The position of the cells of this 

 fifth longitudinal row relatively to those of the four sur- 

 rounding rows, leads to the conclusion that the axile row 

 of cells is formed by the division of the cells of one of the 

 primary longitudinal rows into three-sided outer and four- 

 sided inner cells by means of septa parallel to the chord of 

 the arc of the free outer surface ; a process analogous to the 

 development of the axile string of cells in the neck of the 

 archegonia of liverworts and mosses. This formation of 

 axile cells frequently does not extend throughout the whole 

 length of the organ. It is sometimes suppressed in the 

 cells immediately adjoining the embryo-sac (PI. XXV, fig. 5). 

 More rarely it occurs only in the latter cells, in which case 

 the upper part of the neck of the archegonia consists of 

 four, and its lower part of five rows of cells. Immediately 

 after the formation of the axile string, the contents of the 

 cells are found to be of a grumous nature, and the trans- 

 verse septa which separate the individual cells are soft and 

 gelatinous. When treated with a solution of glycerine, or 

 with any substance which abstracts water, the cells become 

 contracted, and form granular mucilaginous matter, some- 

 times in separate spherical lumps, sometimes in the shape 

 of a single vermiform body (PI. XXV, fig. 8). I attribute 

 the formation of the similar masses which occur in the 

 canals of the necks of archegonia which are approaching 

 maturity, to a similar transformation of the axile string 

 during the further normal development of the archegonia 

 (PL XXV, fig. 11). 



Quite as often however, or even oftener, the formation 

 of an axile row of cells in the neck of the archegonium is 

 suppressed. Both forms of archegonia occur upon pro- 

 thallia of the same species, and even upon one and the same 

 prothalliura. The one form is as common as the other in 

 Pteris serrulata and Ceratojpteris thalictroides. In Aspi- 



