126 H0FME1STER, ON 



cell into four masses, each of which becomes a spore, and 

 also the origin of the elaters, out of a previously thin-coated 

 elongated cell (1. c, pp. 371, 382). In a treatise more par- 

 ticularly devoted to systematic questions relative to the 

 Marchantieae, Bischoff (' Nova Acta A. C. L.,' xviii, 1835) 

 has communicated some interesting results ; he proved 

 that the presence of male plants of Imnularia vulga- 

 ris \% necessary for the development of the fruit (p. 925) ; 

 he pointed to the simple nature of the structure of the first 

 shoot of the germinating spore in comparison with that of 

 the shoots of the fully developed plant (p. 953). He lias 

 repeatedly and emphatically dwelt upon this point, and has 

 endeavoured to distinguish these first shoots (as a prothal- 

 lus) from the later ones (' Handb. Bot. Term./ ii, p. 733 ; 

 'Bot. Zeit.,' 1853, p. 113), starting manifestly from the 

 supposition that the formation of a prothallus is peculiar to 

 the order Muscincae, and that it must, therefore, be proved 

 to exist generally in all liverworts (see BischofFs definition 

 of the Muscineae in C N. A. A. C. L./ xviii, p. 958). Both 

 Gottsche and myself have proved that there is no essential 

 difference between the first shoot of the germ-plant and 

 the later shoots ('Botan. Zeit.,' 1858, Supp., p. 45). 



This difference of opinion can give rise to no real con- 

 troversy. The formation of a prothallus is a universal phe- 

 nomenon in the embryonal life of plants. The development 

 of the germinal vesicle of the phaenogams into the embryo, 

 of the germinal vesicle of the vascular cryptogams into the 

 rudiment of the leafy plant, and of the germinal vesicle of 

 the Muscineae into the fruit all commence with a kind of 

 cell-multiplication, which, at least during the first process 

 of division, differs from the later stages of development. 

 The first, at least, of the permanent cells thus formed does 

 not enter into the composition of the mass of the organ 

 which is to be constructed ; very frequently it dies. The 

 same law prevails in the germination of the spores of ferns 

 and of the Muscineae. In the leafless Jungermannieae, the 

 Riccieae, and the Marchantieae, however, the boundary 

 between the prothallus and the developed plant is not, as 

 Bischoff considers, to be looked for at the point where the 

 second shoot is attached to the first, but at the point where 



