HEP A TiCm. 



299 



Fig. 214. — Anterior margin of the young 

 antheridial disc of Marchaittia polymor- 

 pha ; r the growing margin ; a, a, a the 

 antheridia in different stages of develop- 

 ment ; s/i the stomata above the air-cavities 

 between the antheridia (after Hofmeister, 

 X300). 



under side, and thus forming inflorescences distributed monoeciously or dioeciously. 

 There is a general tendency in the thalloid Hepaticae for the sexual organs to be 

 depressed into hollows by overarchings of the surrounding tissue, and often opening 

 externally only by a narrow mouth. An example of this is given in Fig. 214. 



In the foliose Jungermannieae the origin of 

 the antheridia and archegonia is very various, and 

 they are also enveloped in different ways. Further 

 reference will be made to this in describing the 

 different families. 



The Anther idium consists, in the mature state, 

 of a pedicel surmounted by a globular or ellipsoid 

 body; in those which are imbedded in the tissue 

 the former is usually short, in the free forms it is 

 long, and composed of from one to four rows of 

 cells. The body of the antheridium consists of a 

 wall formed of a single layer of cells containing 

 chlorophyll ; the whole of the space enclosed by 

 it is densely filled by the mother-cells of the an- 

 therozoids ; their escape is occasioned by the ac- 

 cess of water and separation of the cells of the 

 wall at the apex ; sometimes, as in Fossombronia, 

 these cells even fall away from one another. The small mother-cells of the 

 antherozoids which escape in great numbers, separate in the water ; the an- 

 therozoids become free, and have the appearance of slender threads curved 

 spirally from one to three times, and provided at the anterior end with two long 

 very fine cilia, by means of which they move in the water with a rotating motion. 

 Usually they drag after them at the posterior end a small delicate vesicle, the origin 

 of which Strasburger traces to the central vacuole in the protoplasm of the mother- 

 cell, in the periphery of which the antherozoid has been formed. 



The succession of cell-divisions in the formation of the antheridia has been 

 shown by the researches of recent observers to present great diversities in the 

 different genera; they agree, however, in the antheridium always making its first 

 appearance as a papillaeform swelling of a cell from which it is separated by a 

 septum. This papilla thus detached again divides into a lower and an upper cell, 

 the former of which produces the pedicel, the latter the body of the antheridium 

 (parietal layer and mother-cells of the antherozoids). 



There is also some doubt as to the succession of cell-divisions in the formation 

 of the archegonia, since the observations of Leitgeb on Radula and those of Kny 

 and Strasburger on Riccia and Marchantia do not entirely agree. An ultimate 

 agreement may however be expected, since, on the other hand, Leitgeb's history 

 of the development of the archegonia of Radula coincides with that studied by 

 Klihn and Schuch in the Mosses ^ It is certain that the archegonium, like the 



^ [Janczewski has made a series of comparative researches into the development of tlie archego- 

 nium of Muscinetc, Bot. Zeitg. 1872, p. 869 et seq. — Ed.] 



