REPRODUCTION, VEGETABLE (VEGETABLE OVUM). 



58. First period.* From the germination 

 of the spore arises a tubular filament, which 

 is converted directly, by successive divisions, 

 into a simple riband-like frond, with a notch 

 in its anterior margin, containing a young 

 shoot. At whatever age the plant be ob- 

 served, the actively growing portions are 

 shoots which resemble the spore plant in 

 form and structure, and it is at various 

 points of the upper surface of these shoots 

 that the reproductive organs are developed. 



59. The development of the antheridia com- 

 mences in the still very young shoot, by the 

 separation "of a circular group of about sixteen 

 of the superficial layer of cells from those of 

 the tissue below it. There results a small 

 lentil-shaped lacuna in the parenchyma, which 



Fig. 155. 



Section of young shoot of Anthoceros levis, passing 

 through the lacuna in which the antheridia are deve- 

 loped. The rudiments of the antheridia springing 

 from its floor, project upwards into its cavity. 50 

 diam. 



is filled with watery fluid, and roofed over by 

 the cellular layer above mentioned." Each of 

 the cells forming the floor of the lacuna, is 

 divided by two septa, one parallel to the axis 

 of the frond, and perpendicular to its surface, 

 the other also perpendicular, but cutting the 

 first at riijht angles. The membrane of each of 

 the resulting small cells buds out upwards, so 

 as to project into the lacuna, and soon after, 

 the upper projecting portion is cut off from 

 the rest by a transverse septum, and becomes 

 the parent cell of the antheridium. A second 

 septum is then formed above the first, and 

 parallel to it. This is succeeded by a third, 

 which is inclined to the horizon at a small 

 angle. Above it is a fourth, similarly inclined, 

 but in the opposite direction ; next follows a 

 fifth, parallel to the third, and so on alter- 

 nately. In this manner is formed a cylindrical 

 papilla, consisting of two vertical series of cells, 

 each of which is a segment of a cylinder. Each 

 is next bisected by a radiating vertical septum, 

 so that the papilla is now formed of four in- 

 stead of two vertical columns. The penul- 

 timate cell of one of these columns next 



* The following description is abridged from 

 Hofmelster in loc. cit. pp. 4 9. 



233 



divides by a vertical septum, parallel to a 

 plane touching the centre of its outer sur- 

 face. This meets the perpendicular wall 

 last formed at 45, and divides the cell 

 into an external tetrahedral, and an internal 

 three-sided compartment. The latter divides 

 twice by septa, which cross each other at 

 right angles, so as to form a central group, 

 which, as it rapidly enlarges, causes the four 

 less actively growing cells by which it is sur- 

 rounded to assume a tabular form. In its 

 further development it is converted into a 

 mass of very numerous and minute regularly- 

 arranged tessellar cells, in each of which is 

 found " a lentil-shaped vesicle which occupies 

 the greater part of its cavity." Shortly before 

 the antheridium arrives at maturity, the mem- 

 brane of the cells disappears ; the vesicles 

 float free, and there is now found rolled up in 

 each, a spiral fibre of from 2% to 3 coils, which 

 is coloured yellow by iodine. The ripe 

 antheridium presents the. general form and ap- 

 pearance shown in fig. 156. The cellular mem- 



Fig. 156. 



a, diagram of antheriditun of the same, 250 diam. ; 

 b, lenticular cellules containing antherozoids, 600 

 diam. 



brane, resulting from successive division of the 

 four cells, which originally surrounded the 

 central mass, gives way at the apex of the 

 organ. In the meantime, the layer of cells 

 which roofed over the lacuna has split open. 

 The escaped spiral filaments (antherozoids), 

 as seen under the microscope, soon after lose 

 the vesicles in which they were enclosed ; 

 " each slowly revolving round its own axis, 

 lazily progresses in the surrounding water." 

 60. The development of the archegonia in An- 

 thoceros differs from that of all other Hepaticae 

 in its much greater simplicity. A single row 

 of cells commencing at the upper surface of 

 the young shoot, and directed towards its 

 interior, becomes distinguished from those 

 surrounding it by the quantity of granular 

 mucus which it contains. The lowest cell of 

 the series becomes larger than the rest. In 

 its interior a daughter cell (germ-cell) which 

 nearly occupies its cavity, is formed around a 

 pre-existing central nucleus. The contiguous 

 walls of the cells forming the remainder of the 

 series are absorbed. Hence results a canal 

 which leads from the surface to the cavity of 

 the basal cell. It is difficult to believe that 

 an arrangement so remarkable can have any 



