Jennings: Manual of Mosses 3 



open by four, lateral, vertical slits which, however, do not reach the apex. 



The Bryales comprise by far the greatest number of the mosses. The 

 capsule in the Bryales varies from globose to ovate or pyriform or elongated 

 cyhndric. The cells which give rise to the spores are known collectively as 

 sporogenous tissue and this tissue occupies but a small portion of the volume 

 of the capsule, being arranged in the form of a hollow tube or cylinder vertically 

 placed and open at both ends. The sterile tissues occupying the hollow part 

 of this tube constitute the cohunella. The outer wall of the capsule usually 

 contains more or less green chlorophyll and the middle portion of this wall is 

 more or less loosely arranged and contains hollow spaces. The capsule is 

 covered by an epidermis, perforated by stomata in most mosses. The stomata 

 are usually most highly developed on the rounded or tapering base of the 

 capsule which is often more cr less distinct and is known as the collum or neck- 

 In the ripening of the capsule the sterile tissues of the wall and of the columella 

 largely disappear, leaving the capsule filled with a mass of spores. In some 

 species the thin wall of the capsule bursts irregularly, this type of dehiscence 

 being known as cleistocarpous. In other species the top of the capsule sep- 

 arates as a ltd or operculum. The separation of the lid is often facilitated by 

 the modification of a series of epidermal cells termed the annulus, which usu- 

 ally becomes highly hygroscopic and is often deciduous. The sterile tissues 

 immediately beneath the lid are usually more or less highly modified to form 

 a single or double series of pointed structures known collectively as the 

 peristome. The pointed structures constituting the outer series in the double 

 peristome or the single series in a simple peristome are known as teeth, while 

 the inner and more delicate series of the double peristome are known as 

 segments. Between the individual segments in many species of mosses are very 

 delicate hair-like structures known as ctlia. Sometimes the cilia are in groups 

 of two or more alternating with the segments. The peristome is usually very 

 hygroscopic, curling inward and closing the mouth of the capsule in damp air 

 and opening outward and allowing the free dispersal of the spores in dry air. 

 Species whose capsules stand vertically 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 Tem- 

 perate 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 accumulation 

 of the encircling mats around ponds and small lakes tending to fill them also. 

 The mats hold water like a sponge and, being somewhat antiseptic, the dead 

 portions below the mat do not decay but become converted into peat, which, 

 especially in certain parts of Europe, has served a very important purpose as 

 fuel. A considerable number of Sphagnum bogs and Sphagnum cranberry 

 glades of limited area occur in the mountains of central Pennsylvania. The 

 only other bogs of any considerable extent in our region are those m the 



