24 DOUGLAS HOUGHTON CAMPBELL ON THE 



"While the neck-cells are growhig, the central cell of the young archegonium is also 

 undergoing changes. The wall by which it was separated fi-om the primary neck-cell 

 becomes moi-e decidedly convex and pointed, pushing up between the four rows of neck- 

 cells. About the time that the first transverse septa are formed in the neck-cells, the 

 upper pointed part of the central cell becomes cut off by a septum which is concave up- 

 ward, from the main part of the cell (PI. 5, fig. 2). The upper cell becomes the canal- 

 cell of the neck; the lower, the central cell, from which finally the germ-cell is formed. 

 Although a very lai'ge number of archegonia in all stages of development were exam- 

 ined, no trace of any further division of either central cell or canal-cell could be detected 

 beyond the presence in the latter of several nuclei, it appearing probable that in this case, 

 at least, the so-called ventral canal-cell of Janczewski does not exist. 



In its earlier stages the canal-cell is sometimes quite conspicuous, but as it becomes 

 older its outlines are not so definite. The protoplasm is colorless and densely granular, 

 and frequently several nuclei can be detected but no division-walls, except the first one 

 by which it is shut oft' from the centi'al cell. It continues to elongate as the neck of the 

 archegonium grows, reaching as far as the base of the upper cells. "When the arche- 

 gonium is ripe, the wall separating the canal-cell from the central cell becomes muci- 

 laginous, and probably also the iinier layers of the walls of the neck-cells, in a manner 

 analogous to that described in the case of the antheridium. If now water is applied, the 

 walls of the cells dissolve and the space occupied by the neck-cell becomes filled Avith a 

 colorless mucilage derived from the disintegrated cell-walls, together with the protoplasm 

 of the cell. This change is accompanied by active movements of the contents of the canal, 

 the movements l^eing very marked and lasting for about a minute. This was observed oidy 

 in a single instance, but from the resemblance to what takes place in the antheridium, is 

 probably the noi-mal process. After the movements had ceased it was seen that the more 

 solid portions of the contents of the neck had collected in a row of two or three pi-etty 

 distinct masses, the lower one of which was somewhat rounded, corresponding in ap- 

 pearance with Sach's figure of the central canal-cell (PL 5, fig. 6). It is possible that 

 this, which is undoubtedly only part of the contents of the canal-cell, may from its ap- 

 pearance have been considered as a separate cell. There is not always, however, this sep- 

 aration of the granular part of the contents, but in many cases the contents appear the 

 same throughout. 



Probably at the same time that the change described in the neck-cells takes place, but 

 which could not be determined Avith absolute certainty, the contents of the central cell, 

 which have hitherto been uniform, undergo a change. The protoplasm contracts into a 

 sp)herical mass which does not completely fill the central cell; this is the germ-cell or 

 oosphere. It contains a large central nucleus and in favorable cases a transparent area 

 can be detected lying on the side nearest the neck, this being the receptive spot ; the rest 

 of the protoplasm is colorless but densely granular. The central cell increases in size 

 but little from the time it is first formed; it is surrounded by a single layer of small cells 

 cut off from the adjacent cells of the prothallium including the basal cells of the arche- 

 gonium, which usually becomes divided into two nearly equal cells, but otherwise is im- 

 changed in appearance and easily identified. Thus the basal part of the archegonium is 

 completely embedded in the prothallium,- the neck alone projecting beyond the surface. 



