56 HOJfMEISTER, ON 



tion of the cells takes place exclusively in the direction of 

 one surface, with the exception of a single division of all 

 the cells which takes place by septa parallel to the surface, 

 sometimes at this period (PI. XI, fig. 21), and sometimes 

 rather later. The underside of the flat expansion sends out 

 rootlets with very narrow cavities, exactly similar to those 

 produced from the lower leaf-lobes of fully developed plants. 

 The cells of the margin, as well as those of the middle, 

 multiply continually by division caused by septa perpendi- 

 cular to the surfaces of the plate-shaped body (PI. XI, 

 figs. 23, 24). Ultimately, five months after sowing, a 

 small protuberance of cellular tissue is seen at the margin 

 of the flat germ-plant, which is soon recognised as the 

 first commencement of the leafy stem by the fact of its 

 producing rudimentary leaves under its apex (PI. XI, figs. 

 25, 26). The arrangement of the cells of the terminal 

 bud of the young stem shows clearly that its longitudinal 

 growth is the result of the continual division of an apical 

 cell by alternately-inclined septa (PL XI, fig. 26). 



The normal mode of cell-multiplication in the growing 

 end of the stem of developed plants of the leafy Junger- 

 mannise, is most difficult to ascertain. The terminal bud 

 protrudes very slightly above the place of origin of the 

 youngest leaf; the older leaves embrace the bud more 

 closely than in any other plants I know. Numerous hairs 

 which are developed upon and between the youngest leaves 

 interfere with the observation ; the contents of the youngest 

 cells (viz. a thick mucilage in which numerous, often closely- 

 packed chlorophyll bodies are imbedded) are almost opaque ; 

 all which matters present almost insuperable obstacles to 

 the observer. With the exception of the instances brought 

 forward in treating of the germination, there have been but 

 few cases in which I have arrived at clear results, viz., 

 in Frullania dilatata (PI. XI, fig. 9, 10), LopJtocolea biden- 

 tata (PL IX, fig. 13), Trichocolea tomentella (PL VIII, 

 fig, 4), and Jmigermannia bicuspidata (PL VIII, 12, " b ) ; the 

 shoots here examined were the few-leaved shoots which 

 break out between the leaves, and which originate from 

 adventitious buds. They all agree in essentials with one 

 another, as also with the modes of development of the nidi- 



