12.2 IIOFMEISTER, ON 



pears in drops of considerable size upon the upper surface 

 of the antheridial disc. The spermatozoa, which are hardly 

 half as large as those of Pellia, consist of a delicate 

 thread, slightly thickened at one end, and drawn out into 

 a thin long process at the other. I could perceive no trace 

 of lateral cilia.* 



I have only been able to examine the antheridia of 

 Rebomllia hemispherica when fully developed. They are 

 imbedded, as Eischoff's beautiful observations have shown,-r 

 in half-moon-shaped cushions, which appear superimposed 

 upon the median line of vegetative shoots, usually upon 

 those which bear a fruit-receptacle. As the outside of these 

 cushions often bear rudimentary leaves, it appears to me 

 probable that these cushions may be considered to be weakly 

 developed shoots, resembling to some extent, in their deve- 

 lopment, the portions of the stem of Pellia which bear 

 archegonia (PI. XVI, fig. 17). The antheridia are pro- 

 portionably large, surrounded by flask-shaped cavities. In 

 the youngest which I have examined there was still to be 

 seen the covering layer of tabular cells (PI. XVI, fig. 17), 

 which, at a later period, is entirely supplanted, so that a 

 membranous sac alone encloses the cells which produce the 

 spermatozoa. The mouth of the antheridial cavities is 

 not often on the level, like that of Marchantia polymorplia 

 (PI. XVI, fig. 17). It more frequently protrudes to a consi- 

 derable height, in the form of a thick, conical point, like the 

 antheridial envelopes of Riccia. The tissue of the anthe- 

 ridial cushions consists of very large cells, with transparent 

 fluid contents. 



The history of our knowledge of the Marchantiese is 

 most fully treated in Bischoff's work, already so often cited, 

 and in the fourth part of the ' Naturgeschichte Euro- 

 paischer Lebermoose,' by Nees von Esenbeck. Except this 

 volume, I know of no connected treatise on the develop- 

 ment of the March antiese since the almost contemporane- 

 ous appearance of BischofT's and Mirbel's \ large works. 



* Compare Thuret, ' Ann. d. Sc.,' iii ser., torn. 3, pp. 13, 14. 

 f ' N. A. A. C. L.,' vol. xvii, pi. lxix, f. 4, 6, 7. 



% " Rechcrehes sur la Marchantia polymorplia," 'Mem. de 1'Acad. des Se. de 

 1'Iiist. de France,' vol. xiii. 



