396 



BOTANY 



their growth from year to year, while the lower portions die away and become 

 eventually converted into peat. Of the numerous lateral branches arising 

 from each of the shoots, some grow upwards and form the apical tufts or heads 

 at the summits of the stems ; others, which are more elongated and flagelliform 

 in shape, turn downwards and envelop the lower portions of the stem (Fig. 329, 

 A). Every year one branch below the apex develops as strongly as the mother 

 shoot, so that the stem thus becomes falsely bifurcated. By the gradual death 

 of the stem from below upwards the daughter shoots become separated from 

 it, and form independent plants. Special branches of the tufted heads, either 



em 



Fig. 329. — Sphagnum fimiriahim. A, A shoot with four ripe sporogonia. Spliagnum acutifolium- 

 B, Archegonium with the multicellular embryo of the sporogonium cm ; C, a young sporo- 

 gonium in longitudinal section ; ps, pseudopodium ; ea, archegonial wall or calyptra ; ah, neck of 

 archegonium ; spf, foot of sporogonium ; k, capsule ; co, columella ; spo, spore-sac with spores ; 

 E, ruptured antheridium with escaping spermatozoids ; F, single spermatozoid, highly 

 magnified. Sphagnum squarrosum. D, A lateral shoot with a terminal sporogonium ; ca, 

 ruptured calyptra ; d, operculum. (After W. P. Schimper ; A, nat. size ; the other figures 

 magnified.) 



on the same plants (monoecious) or on different stocks (dioecious), are distinguish- 

 able by their different structure and colour ; on these the sexual organs are pro- 

 duced. The male branches give rise, near the leaves, to spherical stalked antheridia, 

 which open at the apices by means of retroflexing valves, and let free the spirally 

 twisted spermatozoids (Fig. 329, E, F). The arohegonia are borne at the tips of 

 the female branches. After fertilisation, the multicellular embryo of a sporogoni,um 

 {B) is produced from the egg-cell. The sporogonium develops a short stalk with 

 an expanded foot (C), but remains for a time enclosed by the archegonial wall or 

 calyptra. Upon the rupture of the archegonium, the calyptra persists just as in 

 the ITepaticae at the base of the sporogonium. The capsule is spherical and has 



