158 HOFMEISTER, ON 



of the cells of the circumference by transverse septa first 

 occurs after the production of an entire row of vertical 

 septa, so that the string of elongated cells in the axis 

 of the organ is far thicker. Even in vigorous specimens 

 of Phascum, a division by a septum parallel to the chord 

 of the arc of the outer surface precedes the formation of 

 horizontal septa in the outer cells. 



The above account of the division of the cells of the 

 second degree does not apply in its entirety to the oldest 

 of such cells. In the latter the above cell-multiplication 

 proceeds only to a certain point ; in the first two, three, 

 or four of such cells, only the radial vertical septum is 

 formed, and in the two three-sided cells thus produced, a 

 tangential septum only ; in the next the formation of radial 

 vertical septa occurs in the four cells of the circumference, 

 and the eight cells thus formed divide by septa cutting 

 the last-mentioned septa at an angle of 90°. Thus the cell- 

 multiplication progresses gradually upwards. 



The thickness of the fruit-rudiment increases conse- 

 quently from below upwards ; it assumes the form of 

 a spindle-shaped cellular mass. As long as the multi- 

 plication of its apical cell continues, the active increase of 

 the cells in the direction of the thickness is always arrested 

 for some considerable distance beneath the apex (PL XXI, 

 %. 3, 3*), 



In the mean time the cells of the ventral portion of the 

 archegonium increase actively : so far as they encircle 

 the fruit-rudiment this increase takes place only by divi- 

 sion by means of septa perpendicular to the outer surface, 

 but in the lower portion it is produced by septa turned 

 in all three directions. The cells also of the hitherto fiat end 

 of the stem which bears the archegonia (both the impregna- 

 ted and the unimpregnated),* expand and multiply actively, 

 those in the middle more actively than those at the sides. By 

 this means the end of the stem becomes conical ; it bears at 

 its apex the impregnated archegonium, and on its inclined 

 surface the abortive archegonia and the paraphyses. This is 



* In several species of Milium, which exhibit a very large number of arche- 

 gonia (as many as fifty) in one inflorescence, several archegonia are usually 

 impregnated. 



