HEPATIC A K. 151 



gonium, which grows in size as the sporogonium grows, and from this time bears the 

 name of calyptra ; it is only in Atifhoceros, where the archegonia are sunk in the 

 thallus, that a proper calyptra is not formed. The stalk of the sporogonium some- 

 times penetrates into the tissue of the vegetative body of the first generation ; papillae 

 shoot out from it, especially in the Anthoceroteae ; these like the papillae of roots 

 are concerned with the supply of food. 



The outer form and the structure of the sporogonium is very different in 

 different groups. In the Anthoceroteae it is in the mature state an elongated pod, 

 which projects above the thallus and opens by two valves ; in the Riccieae it is a thin- 

 walled capsule quite filled with spores and with the calyptra sunk in the thallus ; in 

 the Marchantieae it is a shortly stalked sphere, which encloses elaters as well as 

 spores, and either bursts irregularly after it has broken through the calyptra, or opens 

 by a circular slit from which a lid falls off; in the Jungermannieae it matures as in 

 the other families inside the calyptra, but ultimately breaks through it and appears as 

 a sphere on a long and delicate stalk. The capsule when mature consists in the 

 Jungermannieae, as in the Marchantieae and Riccieae, of a single layer of cells, but 

 it opens by four stalked lobes disposed crosswise, on which the elaters remain 

 suspended. The elater here, as in the IMarchantieae, are long fusiform cells, with 

 one to three brown spiral bands as thickenings on the inside of the stout colourless 

 outer layer of the wall. 



The course of development of the sporogonium is marked by not unimportant 

 variations in the several groups, in connection especially with the origin of the tissue 

 which produces the spores, i. e. the differentiation of the archesporium, while there is a 

 general agreement among them with regard to the course of cell-formation in the 

 embryo. There is at the same time a continuous series within the group of the 

 Hepaticae from the simple embryo of the genus Riccia to the more highly developed 

 embryo of the Anthoceroteae. The embryos of Riccia (Fig. loi. A) are spherical 

 and divided at first into octants. Further divisions then appear by which a 

 peripheral layer of cells, the wall of the sporogonium, is separated from the central 

 tissue, which becomes in its entirety spore-mother-cells, and each of these cells pro- 

 duces by division four spores. The wall of the capsule eventually decays. But 

 further differentiations are found even among the Riccieae. Sterile cells, not em- 

 ployed in the formation of spores, which may be regarded as analogous to elaters, 

 are found in Corsinia, and the genus Boschia has undoubted elaters ; and in these two 

 genera, as in the nearly allied Marchantieae, there is already a distinction in the 

 sporogonium between stalk and capsule. This distinction is introduced in the 

 Marchantieae (but not in the two genera of the Riccieae just mentioned according 

 to Kienitz-Gerloff) by the first wall formed in the oospore which is at right angles 

 to the axis of the archegonium (Fig. loi, B) ; the upper cell, which is towards the 

 neck of the archegonium, developes into the capsule, the lower forms the stalk which 

 is as yet but small. Here too, as in Riccia, the young embryo divides into octants, of 

 which the four upper become the capsule, consisting of a layer of cells forming 

 the wall and the inner cells from which the spores and elaters proceed. The elaters 

 have pointed extremities and lie between the single or double rows of the spore- 

 mother-cells. In the Jungermannieae the oospore is first divided by a wall at right 

 angles to the axis of the archegonium into a lower and an upper cell ; both the capsule 



