298 HOFMEISTER, ON 



(according to repeated experiments) only female pro- 

 thallia. 



The archegonia are produced by the multiplication of 

 individual cells of the fore-edge of the thick, fleshy lobes 

 of the pro-thallium. After the commencement of the form- 

 ation of the archegonium the mass of cellular tissue to 

 which the organ is attached usually continues to grow 

 underneath it, so that the archegonia, like those of Pellia, 

 are afterwards situated on the surface of the prothallium. 

 A small, thin, membranous shoot of the prothallium is 

 usually formed near each archegonium (PI. XL, fig. 1). 



The mother-cell of an archegonium which, like its neigh- 

 bours, contains chlorophyll, only differs from the latter by 

 its greater abundance of protoplasm. After its free upper 

 wall has become considerably curved, its first division takes 

 place by a horizontal membrane. The lower of the two 

 halves, which is entirely sunk into the tissue of the pro- 

 thallium, becomes the central cell of the archegonium, the 

 aperture of the latter being formed by repeated bi-parti- 

 tions of the upper half. 



The first of these partitions takes place by a vertical 

 longitudinal septum. Another septum, also vertical and at 

 right angles to that just formed, appears immediately in 

 each of the two newly formed cells. The four cells sur- 

 rounding the central cell, which in the mean time has be- 

 come remarkably curved above, grow uniformly upwards, 

 and are at the same time divided by horizontal transverse 

 septa exactly in the same manner as the four vertical-cells 

 of the fruit rudiment of a Jungermannia.* Thus a cylinder 

 is formed projecting above the central cell of the archego- 

 nium, composed of four longitudinal rows of cells (PI. 

 XXXVII, figs. 35 37). The upper pair of cells undergoes 

 considerable elongation, which afterwards takes place also 

 in the next adjoining pair, though in a less considerable 

 degree. The two lower pairs of cells of the neck of the 

 archegonium become elongated upwards, but hardly per- 

 ceptibly so; however, the incipient multiplication of the 

 cells adjoining the central cell extends to the two lower 

 pairs of cells, or at least to the lowest of them, the division 

 taking place by means of septa alternately perpendicular 



* 'Vergl. Unters.,' pp. 18, 38. 



