338 INTRODUCTION TO CRYPTOGAMIC BOTANY. 



the peridium iu some sjDecies of Gribraria. In Reticularia, 

 tliis flattening and expansion of the threads are carried to 

 the greatest extent. When the spores are all dispersed, the 

 processes which remain attached to the base look like a 

 number of erect lacerated chaffy scales, resembling those 

 with which the pilei of some Hymenomycetes are clothed, 

 though not so rigid. In Aoigioridium they appear like 

 thin shapeless chalky shreds, by contrast with the dark fruit 

 with which they are intermixed. In Trichia, the threads, 

 which are either simple or branched, contain one or more 

 spirals, a structure first noticed by Schmidel, and more fully 

 demonstrated by Hedwig the younger, and in modern times 

 by Corda. Some doubt has lately been expressed on this sub- 

 ject ; but the best microscopes certainly show one or more 

 internal spiral threads. In some instances, the external mem- 

 brane is studded with asperities, to which, perhaps, the spores 

 were originally attached, but this is uncertain. In Arcyria, 

 which comes so near to Trichia, there are peculiar asperities of 

 a somewhat similar nature, confined to one side of the threads. 

 In some cases, very probably, the outer membrane itself may 

 have a spiral structure, as mil be noticed hereafter in Po- 

 daxon. 



364 The spores do not differ very greatly in most of the 

 genera ; they are, however, occasionally echinulate, as in 

 Badhamia, or reticulate, as in Trichamphora (Fig. 75, a). 

 They assume a great variety of colours, generally more or less 

 tinged with red, and sometimes of a pure red or scarlet. 

 They are, for the most part, undoubtedly attached to the 

 threads ; but in two genera, Enerthenema and Badhamia, 

 they form definite groups, surrounded by a common cyst. 

 Sometimes the spores, under such circumstances, are uniform ; 

 but in most instances the exposed side exhibits asperities 

 which do not exist towards the centre of the group, and some- 

 times the external spores are gTouped round a larger central 

 spore. Corda has shown a definite arrangement of the spores 

 in one genus ; and the fact that the spores of Hymcnangium, 

 though essentially borne on sporophores, are sometimes sur- 

 rounded by a sac, forbids our attributing so much consequence 



