IV THE JUNGERMANNIACE/E 72, 



growing spores. The sporogonium remains within the calyptra 

 until the spores are ripe, when by a rapid elongation of the 

 cells of the seta it breaks through the calyptra, which is left at 

 its base, and the capsule then opens. The opening of the 

 capsule is usually effected by its walls splitting into four valves 

 along lines coincident with the first formed vertical cell walls 

 in the young embryo. These valves, as well as the elaters, are 

 strongly hygroscopic, and by their movements help to scatter 

 the ripe spores. The latter show much the same differences 

 observed in the Marchantiaceae. When the spores germinate 

 at once they have abundant chlorophyll and a thin exospore, 

 but w^here they are exposed to drying up, they have no 

 chlorophyll and the exospore is thick and usually with 

 characteristic thickenings upon it. From the germinating 

 spore the young gametophyte may develop directly, or there 

 may be a well-marked protonemal stage. This latter is 

 always found in the foliose forms, and is either a flat thallus, 

 like the permanent condition of the lower thallose genera, or 

 sometimes {Protocephalozia) it is a branched filamentous 

 protonema, very much like that of the Mosses, and sometimes 

 long-lived and producing numerous gametophores. 



Non-sexual reproductive bodies in the form of unicellular 

 gemmae are found in many species, and in Blasia special 

 receptacles with multicellular gemmae something like those of 

 Marchantia occur. 



The Jungermanniaceae naturally fall into two well-marked 

 series,^ J. anacrogynae and J. acrogynse, based upon the position 

 of the archegonia. These in the former are never produced 

 directly from the apical cell of a branch, in the latter group 

 the apical cell of the archegonial branch always sooner or later 

 becomes transformed into an archegonium. The Haplomitrieae 

 show some interesting intermediate forms between the two 

 groups, but all the other Jungermanniaceae examined belong 

 decidedly to one or the other. As a rule the Anacrogynae 

 are thallose (the " frondose " forms of the older botanists), 

 but a few genera, especially Fossoinbronia, show a genuine 

 formation of leaves. All the Acrogynae have a distinct slender 

 stem with large and perfectly developed leaves. 



^ Prof. L. ]\I. Underwood proposes the name Metzgeriaceae for the }• anacrogynae, 

 reserving the name JungermanniaceK for the J. acrogyna;. These two groups he 

 considers co-ordinate with the Marchantiaceae and Anthoceroteae. 



