F. Cavers . 
3 6 
endostome consists of very thin plates, the outer layer corres¬ 
ponding to the inner layer of the exostome. The thickened cell- 
walls that contribute to the formation of the entire peristome 
belong to three concentric layers of cells. As was shown by 
Philibert, the single peristome of the Haplolepideae is the homo- 
logue of the inner peristome of the Diplolepideae. It would there¬ 
fore perhaps be better to apply the term “ haplostome ” to the 
simple peristome of the Haplolepideae and to the inner peristome 
of the Diplolepideae. The endostome of Diplolepideae, however, 
presents much greater variety of form than does the simple 
peristome of Haplolepideae; it sometimes consists of a single series 
of sixteen teeth, but in its typical form it is differentiated into a 
collar-like basal membrane (usually sharply folded or keeled), which 
bears on its margin a series of processes and between these a number 
of fine filaments or cilia. The Diplolepideee are divided into two 
main series, (i.) Epicranoidece. Exostome teeth superposed on the 
endostome processes ; exostome teeth usually undivided, sometimes 
joined basally in pairs, sometimes joined at the tips to a small disc 
(e.g. Funaria), rarely all joined at the base to a narrow membrane; 
endostome not keeled, and lacking both basal membrane and cilia. 
The Epicranoidece are again divided into (a) Funariince (Funari- 
acece and Disceliacece) in which the endostome processes are free, 
and (b) Splachnince (Splachnacece, Oedipodiacece, and Schistosteg- 
acece) in which the endostome is either absent or is coherent with 
the exostome. (ii.) Metacranoidece. Exostome teeth alternating 
with the endostome processes ; exostome teeth usually undivided, 
always free; endostome keeled and differentiated into basal 
membrane, processes, and cilia, but sometimes rudimentary and 
then occasionally united to the exostome, but rarely absent 
altogether. The Metacranoidece, a very large group, are divided into 
(a) Bryince (Mitteniacece, Bryacece, Mniacece, Leptostomacece, 
Rhizogoniacece, Aulacomniacece, Timmiacece/Meeseacece, Bartrami- 
acece, Spiridentacece); (b) Isobryince (Drepanophyllacece, Eustichi- 
acece, Orthotrichacese, Erpodiacece, Cryphceacece, Leucodontacece, 
Pterobryacece, Fontinalacece, Chmaciacece, Hedwigiacece, Meteori- 
acece, Sorapillacece, Neckeracese, etc.); (c) Hookerince (Nemat- 
acece, Pilotrichacece, Hookeriacece, Hypopterygiacece); (d) Hypno- 
bryince (Fabroniacese, Entodontacece, Hypnacece, Brachytheci- 
acece, etc.). These sub-divisions are based partly on minor 
characters of the peristome, partly on vegetative characters of the 
gametophyte. 
