24 HOEMEISTER, ON 



long tube attached to the cell. The mode of origin of the 

 first main root does not differ essentially from that just 

 described ; the conical cell which emits the rootlet usually 

 (not always, see PI. IV, fig. 1.2) becomes transformed by 

 degrees into the main root. 



In consequence of the commencement of the expansion 

 of the basal cell of the germ-plant, the outer membrane of 

 the spore (which, although it has become considerably ex- 

 panded and more delicate, has, nevertheless, up to this point, 

 still enclosed the germinating spore) is ruptured (PI. IV, 

 fig. 10). The debris of this membrane may be found, for 

 some time afterwards, attached to the apex of the young 

 plant (PI. IV, fig. 13). 



By this time, the cells nearest to the fore edge of the 

 young Pellia have begun to protrude short club-shaped 

 hairs (PL IV, figs. 13, 14), which appear in increased 

 numbers as the growth of the plant progresses (PL IV, 

 figs. 24, 27). 



From six to eight weeks after the sowing of the spores, 

 the germ-plant has, partly by the multiplication and partly 

 by the expansion of its cells, attained a length of from \'" 

 to § '". It is now attached to the ground by a larger num- 

 ber of rootlets ; the fore edge, from repeated division of its 

 marginal cells, has become wider than the older parts. At 

 every repetition of a longitudinal division of the marginal 

 cells, the septa, which continue to be perpendicular to the 

 surfaces of the plant, appear to diverge laterally more and 

 more in the fore part of the plant. The consequence is, that 

 the arrangement of the cells (PL IV, fig. 15) is flabelliform. 

 The sides of the fore edge grow more rapidly than its middle, 

 partly on account of a more frequent division of the cells by 

 means of septa inclined alternately in different directions, 

 but principally on account of a more vigorous expansion of 

 the cells. The apex of the young plant appears indented, 

 at first slightly, afterwards more deeply (PL IV, fig. 15). 

 The cell which occupies the bottom of the indentation 

 begins all of a sudden to multiply itself actively. It divides 

 twice by a transverse septum perpendicular to the surfaces 

 of the plant. The foremost of the new cells divides by a 

 longitudinal septum into two, each of which is again divided 



