ACROGEN^. 



ro9 



hiscence of the sporangium, its mouth (stoma) is seen to be 

 either fringed by one or two-rows of teeth (peristome) (Jig. 804, p), 



Fig. 1091. 



or naked (gymnostomous) (Jig. 805). 



Division of the Order, Sfc. — This order 

 is usually separated into two divisions, 

 which are frequently regarded as distinct 

 orders. The principal distinctive charac- 

 ters of the two divisions are as follows : — 



Sub- Order 1. Bryaceoe or Bryecs. — Urn- 

 Mosses. — Sporangium dehiscing trans- 

 versely by the separation of the oper- 

 culum, or irregularly. Examples : — 

 Pottia, Splachnum, Wardia, Bryum 

 Funaria, Polytrichum, Hypnum, Neck- 

 era, Hookeria, Sphagnum. The genus 

 Sphagnum is by Henfrey, made to con- 

 stitute a distinct order, under the name 

 of Sphagnaceae or Bog-mosses ; these 

 are principally distinguished from the 

 Bryacea? in habit, and in the curious 

 structure of their leaves. 

 Sub-Order 2. Andraacece or Andraece. 

 — Split- Mosses. — Sporangium splitting 

 vertically into 4 valves which are con- 

 nected at the summit. Examples : — 

 Andrsea, Acroschisma. These are the 

 only genera in this sub-order. 

 Distribution, ^c. — They are generally 

 diffused over the globe, but most abun- 

 dantly in temperate climates. There are 

 46 genera, and about 1200 species. 



Properties and Uses. — Of little import- 

 ance either in a medical or economic 

 point of view. Some species possess astringent and diuretic 

 properties, but they are not used in medicine. The species 

 of Sphagnum fiu'nish food to the reindeer, and even to man 

 in the polar regions. 



Natural Order 291. Hepaticace^. — The Liverwort Order. 

 — (See pages 378—381.) Small cellular plants, either with a 

 creeping stem bearing minute imbricated leaves (fig. 1092), or 

 v^ath a lobed leaf-like frond or thalloid expansion (^7^5. 808 and 

 810). Reproductive organs of two kinds, called respectively, 

 antheridia and archegonia, which are either on the same plant 

 or on different ones. The antheridia are small, oval, globular, 

 or flask-shaped (fig. 809,) cellular sacs, situated in the axils of 

 leaves, or immersed in the frond, or imbedded in the upper 

 surface of peltate or discoid- stalked receptacles (fig. 808). The 

 z z 4 



Fig. 1091. A portion of j4n- 

 drtea rupestrU, much 

 magnified. The stem is 

 erect, with numerous 

 small imbricated leaves, 

 and a terminal sporan- 

 gium, which is destitute 

 of a seta, o, sporangium 

 after dehiscence, showing 

 the 4 equal valves of 

 winch it is composed 

 connected at the summit 

 by the persistent oper- 

 culum. The valves are 

 seen to have dehisced ver- 

 tically. After Hooker. 



