The Thread-Mosses. 155 



THE THREAD-MOSSES. 



BY M. G. CAMPBELL. 



The thread-mosses are an interesting and numerous tribe, con- 

 taining upwards of fifty species, which have been parcelled out 

 into eight distinct genera ; but as space would fail us to de- 

 scribe them all, we shall, at the present time, only pass in 

 review a portion of the Bryums, the chief genus. 



They appear to derive their generic appellation from the 

 Greek word $pvov ? a moss, which would seem to say they were 

 the first of this tribe of plants that attracted attention, and we 

 can scarcely wonder at this when we behold their dense tufts 

 crowned with innumerable beautifully-formed reddish or bright 

 brown pendulous capsules, like eardrops of cornelian or coral 

 awaiting some fairy hand to give them a golden setting ; at all 

 events the name is of very ancient origin, is found in the works 

 of Dioscorides, the Sicilian physician, and has been applied by 

 Dillenius to this genus and its affinities. 



The mosses of this genus are perennial, have terminal 

 fructification, of a pyriform, club-shaped, or oblong outline, 

 smooth and inclined, pendulous, or sub-pendulous, with a taper- 

 ing neck or apophysis, varying in length according to the 

 species, and terminating a long fruit-stalk. They are found 

 growing on rocks, on stone walls, on the ground, and some- 

 times, but rarely, on the trunks of trees. They have a double 

 peristome, the outer consisting of sixteen equidistant, lan- 

 ceolate, hygroscopic teeth, incurved or connivent when dry, 

 transversely barred, the bars internally prominent, and exter- 

 nally the teeth are marked with a medial line. The inner 

 peristome is a membrane divided half way down into sixteen 

 carinate processes, alternating with the outer teeth. Some- 

 times furnished with, and sometimes destitute of, intermediate 

 cilia, which when present are filiform, and either solitary or 

 two or three together. 



The spores are rather small, smooth, globular, green, or 

 reddish brown. The stem has innovations from the floral apex, 

 which innovations resemble the parent stem, are either simple 

 or branched, are tomentose with radicles, and by their issuing 

 from the floral apex, instead of from the lower part of the 

 stem, form, though not without an exception, one of the cha- 

 racteristic differences between the species apportioned to this 

 genus and those assigned to the Miliums. 



One of the most common examples of this family is 

 the Bryum intermedium, or many -seasoned thread-moss, which 



