(136) 
by spiral threads called elaters. The favorite habitat of 
hepatics is wet places, and mountains continually steeped in 
clouds yield a surprising variety of forms. Closely related 
to the hepatics is the group Anthocerotes; these plants may 
however be distinguished by the presence of a central axis or 
column (columella) in the capsule, and there are several 
other important structural differences in their tissues. 
The mosses (cases 41 to 48) follow the hepatics in order of 
development and complexity ; they differ from them, however, 
in many respects. The stem and leaves have more differen- 
tiated tissues, and the leaves usually have a midvein. The 
moss capsule generally opens by a lid under which there are 
commonly appendages to aid in scattering the spores, which 
in this case are not accompanied by spiral threads as they are 
in the hepatics. The mosses fall into three primary groups: 
First the ‘* peat-mosses” (Sphagnum) which differ from the 
rest of the mosses in the development of the tissue-structure 
of the capsule, and the spores; they grow in swamps and 
other wet places, and their accumulation forms peat. The 
‘‘black mosses” (Axdreaea) differ from both of the other 
groups in the valvular capsule; they grow on dry rocks. 
The true mosses vary exceedingly in size and aspect. An 
examination of the specimens in the exhibition cases will 
convey to the mind a better idea of this group than a descrip- 
tion. They grow under all kinds of conditions from dry 
rocks to deep water. Many of the kinds grow on almost any 
kind of rock, earth or bark of trees, while certain ones are 
more particular as to their habitat. Some will thrive only on 
limestone, which they often gradually disintegrate and parti- 
ally preserve in the masses of closely set plants as a calcare- 
ous tufa; other species prefer ground that has recently been 
burnt over, as species of Hunaria and Leptobryum, while 
others grow only on the bones of dead animals or in places 
where animal refuse has accumulated. 
Next higher in the plant kingdom is the subkingdom Pteri- 
dophyta, or ferns and fern-allies, the seedless plants with roots, 
stems, leaves and woody tissue (cases 49 to 55). The ferns 
