4 A MANUAL OF MOSSES 



of the spores in dry air. Species whose capsules stand vertical- 

 ly are not so likely to have well-developed peristomes as are 

 species whose capsules are inclined or vertical, this variation 

 corresponding to the need for the regulation of spore dispersal. 



The Sphagnales are most abundant in the cooler parts of 

 the North Temperate zone, often constituting there large 

 tracts of Vegetation. By their aquatic or semi-aquatic manner 

 of life and their apical method of growth, dying away below as 

 they grow upward, they tend to form great tufts or mats, often 

 completely filling depressions and bogs and by the accurriula- 

 tion of the encircling mats around ponds and small lakes tend- 

 ing to fill them also. The mats hold water like a sponge and, 

 being somewhat intiseptic, the dead portions below the mat 

 do not decay but become converted into peat, which, especial- 

 ly in certain parts of Europe, has served a very important pur- 

 ix)se as fuel. Although a few Sphagniiiii bogs of limited area 

 occur in the mountains of central Pennsylvania the only bogs 

 of any considerable extent in our region are those in the north-, 

 western part of Pennsylvania, particularly in the Pymatuning 

 Swamp, between Linesville and Hartstown, in Crawford 

 County. Here, in places, the Sphagnum and Tamarack prac- 

 tically reign supreme for acres in extent and the peat deposits 

 are apparently quite deep. As may be seen in the treatment 

 of Sphagnum in this Manual, the Pymatuning Swamp has 

 yielded a goodly share of the species reported for our region. 



No Andreaeales have as yet been reported in our region, 

 although they occur in the mountains both to the south and 

 to the northeast. It is not unlikely that Aitdreaea will yet be 

 found to occur in the mountains of central Pennsylvania upon 

 some of the sandstone ridges. 



The Bryales constitute by far the greater number of moss 

 species found in Pennsylvania. Western Pennsylvania as a 

 whole offers quite a variety of habitats and its moss flora is 

 fairly large, although, considering the area covered, there is a 

 noticeable lack of certain species more or less peculiar to high 

 elevations, to outcrops of limestone, and to low-lying marshes 

 and river swamps. 



The northwestern part of Pennsylvania, in a triangular 

 area extending as far south as Beaver County and as far east 

 as Warren County, was worked over b^ the ice in the Glacial 

 Period and is still in a rather youthful stage of erosion, with 

 a number of small lakes, and ponds and considerable areas of 

 poorly drained lands. Occasional Sphagnum bogs occur kere 

 as well as swamps along the flood-plains of some of the 

 Streams. Such conditions offer suitable habitats for a number 

 of aquatic and swamp-inhabiting species of the Bryales which 

 are not to be found at all or are quite rare in the rest of 



