MARSII.IA VESTITA. I97 



iircheg'onium mother-cell behaves in all respects like that 

 of the ordinary ferns. It divides first into a lower or 

 basal cell, which forms later a single layer of cells, 

 separating the central cell of the archegonium from the 

 spore cavity, and a much larger upper one which forms 

 the archegonium proper. The basal cell divides into two 

 nearly equal cells, and each of these by a similar wall, 

 so that a cross section of the base of a prothallium of 

 about seven hours (fig. lo. b) shows this cell divided 

 into nearly equal quadrants. While this division is pro- 

 gressing in the basal cells, the peripheral cells are also 

 dividing by both vertical and horizontal walls, but only 

 in two planes, so that the central cell is invested on all 

 sides by a single layer of cells. These contain small but 

 distinct nuclei and more or less granular contents, and 

 after fertilization develop more or less chlorophyl. 



From the top of the central cell is now cut off a shal- 

 low cell which later divides into four by two cross walls, 

 very much as the basal cell divides, and this forms the 

 beginning of the neck of the archegonium (pi. iv, fig. 

 II, «). These cells do not at first project, but a little 

 later increase somewhat in size and each becomes divided 

 by an oblique wall into two cells, of which the upper ones 

 become strongly turgescent and project in the form of a 

 papilla beyond the ruptured exospore. which is broken 

 through at about this stage (pi. iv, fig. 12). About the 

 same time that this division takes place in the next cell, 

 a small cell is cut off from the central cell, and forms the 

 next canal cell (fig. 12, c) , and very soon after a second 

 smaller one (fig. 13, b), and very soon after this the con- 

 tents of the central cell contract to form the ^gg. and its 

 walls as well as those of the canal cells become disor- 

 ganized. The Qgg at this stage shows a clear space at 

 the top, the receptive spot (fig. 13, r) , and the nucleus 

 although distinct is unusually small. 



