504 INTRODUCTION TO CRYPTOGAMIC BOTANY. 



from Cryptothecei, in addition to their different habit. They 

 are distinguished from Hypnei by their erect sporangia, to 

 which the exceptions are not important. LeiJtodon Sniithii 

 has the sporangium slightly cernuous, but that is a species 

 which the short peduncle evidently separates from Hypnei. 

 In one or two Leskece also the sporangium is suberect, and 

 the same may be said of Isothecium. I can discover no cha- 

 racters by which Leucodontei can be separated from Isothecii, 

 and therefore both are included here in one tribe. Leucodon, 

 AntitricJiia, Leptodon, and Anomodon are the British 

 genera belonging to the former group, while Pterogonium, 

 Isothecium, Glimaciwm, Cylindrothecium, and Leskea belong 

 to the latter. Most of these genera depend upon modifications 

 of the peristome, and in some cases on slight differences of 

 habit. Leskea, for instance, differs from Hypnumi not only 

 in the erect sporangia, but in the absence of intermediate cilia 

 in the inner peristome. Glmiacium deserves especial notice 

 on account of the tree-like habit of the species, accompa- 

 nied by a peculiarity in the inner cilia, which are distinctly 

 lacunose. Several species of this tribe, especially of the genus 

 Isothecmm, occur in the southern hemisphere, but some are 

 found also in the tropics. Leptodon Smithii is widely distri- 

 buted, Pterogoniura hirtellum has the leaves sprinkled with 

 short hairs, a rare character amongst mosses. 



10. Ehizogoniei, Mont. 



Leaves distichous, perichsetial shoots springing from the 

 base ; calyptra dimidiate ; peristome single or double. 



564. This little tribe consists of two genera, Rhizogonium 

 and Hymenodon, which differ greatly from Hypnum in habit. 

 The stems are for the most part erect, clothed with distichous 

 often margined leaves, and bearing the perichajtial branches 

 only at the very base, as if the moisture at the base of the 

 tufts were necessary for their development. The tribe is 

 therefore analogous to Geocalycece among the Jungermannice. 

 Hymenodon differs in having only a single peristome and a 

 straight sporangium. Six species of Rhizogonium are recorded 

 in the Flora of New Zealand, and one of Hymenodon. Other 

 species occur in Brazil and Java. Rhizogoniwtn spiniforTne 



