BOTANY 



Variations in the form of the capsule, peristome, operculum, and calyptra 

 afford the most important means of distinguishing the different genera. The 

 Bryinae are first divided into two sub-orders, according to the position of the arche- 

 gonia or of the sporogonia developed from them. 



(a) Bryinae acrocarpae. — The archegonia, and consequently the sporogonia, are 

 terminal on the main axis. Milium hornum, the species referred to above (Fig. 

 321), belongs to this group ; it grows in damp places, in woods and at the base of 

 rocky cliffs. Polytrichum commune, a common acrocarpous Moss, which is found 

 abundantly in high latitudes, has a stem often several decimetres long (Fig. 323). 

 The four-sided grooved capsule is borne on a long stalk, with a ring-like apophysis, 

 and is almost completely encased by the brown felted calyptra. The peristome 

 is single and consists of 32 teeth. Funaria hygrometrica, another very familiar 

 example of the Acrocarpae, is found growing on the ground and on walls. The 

 leafy stems of this species are very small ; the oblique capsules are pear-shaped 

 and raised upon a long hygroscopic seta, which becomes spirally twisted when 

 dry, but straightens again if moistened. Schistostega osmundacea, a moss living in 

 caves, has fertile shoots, which have spirally arranged leaves and bear stalked 

 capsules devoid of peristomes, and also other shoots that are sterile, with two rows 

 of leaves (Fig. 324, A, B). The protonema of this species gives out an emerald 

 light (p. 223). Its branched filaments place themselves in a plane perpendicular 

 to the incident rays of light, so that the cells, which are disc-shaped, projecting 

 conically on the under side, reflect the light in the same way as a reflecting mirror 

 (Fig. 325). 



(b) Bryinae pleurocarpae. — The growth of the main axis is unlimited, and the 

 archegonia with their sporogonia arise on short, lateral branches (Fig. 326). In 

 this group are included numerous, usually profusely branched species of large 

 Wood Mosses belonging to the genera Hylocomium, Neckera, and Bypnum, and 

 also the submerged Water Moss, Fontinalis antipyretica. 



Order 2. Phaseaeeae 



To the Phaseaeeae ( Cleistocarpae) belong small Mosses with few leaves growing 

 on the soil ; they retain their filamentous protonemata until the capsules are ripe, 

 and have the simplest structure of all the Mosses (Fig. 327). The hooded capsule is 

 terminal and has only a short stalk. It does not open with a lid, but the spores 

 are set free by the decay of its walls. 



Order 3. Andreaeaeeae 



The Andreaeaeeae (Schizocarpae) comprise only the one genus, Andreaea, small, 

 brownish csespitose Mosses growing on rocks. The sporogonium is also terminal 

 in this order. The capsule, at first provided with a calyptra, splits into four longi- 

 tudinal valves, which remain united at the base and apex (Fig. 328). The stalk is 

 short, and is expanded at the base into a foot (Spf), which in turn is borne on a 

 pseudopodium (ps), a stalk-like prolongation of the stem resulting from its elonga- 

 tion after the fertilisation of the archegonium. 



Order 4. Sphagnaeeae 



The order of the Sphagnaeeae, or Bog Mosses, includes only a single genus, 

 Sphagnum. The Bog Mosses grow in swampy places, which they cover with a 

 thick carpet saturated with water. The upper extremities of the stems continue 



