BBYAOM!^. 



359 



in some cases a development wliich foreshadows tlio difEerentiation of 

 tlie stem into the epidermal, fibro-vascular, and fundamental systems of 

 tlie higher plants. In PolytrieJmm, for example, there can be no doubt 

 that the axial and extra-axial bundles of elongated cells with thickened 

 walls found in the stem represent the fibro-vascular bundles of thfe 

 Pteridophytes and Phanerogams ; the bundles 

 of elongated thin-walled cells which pass 

 downward through the stem from the base of 

 the leaf, in Splachnum, must also be regarded 

 as representing rudimentary foliar bundles. 



While these higher Mosses cannot properly 

 be classed with vascular plants, their tissues 

 in some cases reach so high a development as 

 to show that there is no abrupt change in pass- 

 ing from the so-called non-vascular plants to 

 the vascular ones. 



The inflorescence of Bryaceae is hermaphro- 

 dite, monoecious, or dioecious. The sexual or- 

 gans are situated on the apex of the main 



Fig. 247.— Two capsules 

 of Bryum argp.nieum. The 

 one on the left is still per- 

 fect ; at its apex is shown 

 the lid or operculum ; the 

 , , . r 1 ^ 1 i 1 1 1 one on the right has dropped 



stem (Acrocarpa;), or of short lateral branches its operculum, exposing the 



(Pleurocarpaj). The sporogonium, in its de- {!|'j^j*°™^ ^ 'uifed"°^°" 

 velopment, carries up the old- archei;onium as 



a calyptra, which quickly falls away in some genera {e.g., Bryum, 

 Bartramia, etc.), while in others (e.g., Polytrkhum, Pogonatam, etc.) it 

 persists as a closely fittins; covering of the capsule ; between these 

 two extremes there are all gradations. 



Tlie sporogonium is usually long stalked (Fig. 

 346, B). The capsule is generally more or less 

 ovoid or cylindrical. It is at first composed of pa- 

 renchymatous tissue, which entirely fills up its 

 interior; as it enlarges, however, an annular in- 

 tercellular air cavity forms, separating a cylin- 

 drical axial portion from tlie outer portion, which 

 forms the wall of the capsule. The axial cylin- 

 der remains in connection with the remainder 

 of the capsule at its top and bottom (t, Fig. 346, 

 G), and it is, moreover, slightly connected with 

 the capsule walls by chlorophyll-bearing confer- 

 void filaments, which pass across the air cavity. 

 The rather dense tissues below and surrounding 

 the air cavity in the immature capsule are com- 

 posed of chlorophyll-bearing cells, and the epidermis covering these 

 portions is supplied with stomata. The spores are developed from a 

 layer of cells (the third or fourth from the outside) in the axial cylinder 

 (s, Fig. 346, 0) ; and each cell of the spore-bearing layer produces four 

 rspores. The portion of the axial cylinder within the spore-bearing 



Fig. 248.— Apical 

 part of the capsule of 

 FontinalU antipyre- 

 tica. showing the 

 double peristome. The 

 outer row is made up 

 of teeth, the inner of 

 ■cilia. Magnified. 



