1 84 



SECOND GR UP. M US CINE A E. 



of which form a bud-like envelope ; the young perichaetial leaves too are inclosed within 

 this envelope at the period of fertilisation, and afterwards grow to a larger size. The 

 archegonia are exactly like those of the rest of the Mosses ; the oospheres of several 

 archegoniain a perichaetium are usually fertilised, but only one matures its sporogonium. 

 The sporogonium comes to maturity inside the perichaetium, and it is not till then that 

 the summit of the branch elongates and becomes a long naked stalk, and raises the 

 sporogonium in its calyptra high above the perichaetium ; this organ, which is called 

 the pseudopodium, must not be confounded with the seta of other Mosses. Fig. 139, B 



gives a longitudinal section of a nearly mature 

 sporogonium inside the calyptra. Its lower portion 

 is developed into a thick foot sunk in the top of 

 the pseudopodium, where it forms the vaginula . 

 A hemispherical layer of cells beneath the apex of 

 the globular capsule is used to form the spore- 

 mother-cells ; the part of the inner tissue beneath 

 this layer forms a low nearly hemispherical column, 

 which is called the columella, though it differs from 

 the columella of the true Mosses in not reaching 

 to the apex of the capsule. The spores are formed 

 from the mother-cells in the same way as in the 

 true Mosses ; but in addition to the ordinary large 

 spores there are found other smaller spores in 

 special smaller sporogonia, which owe their origin 

 to further division of the mother-cells, and are 

 probably only deformities (Fig. 133, B}. The 

 capsule opens by removal of a lid, the uppermost 

 segment of the sphere, which is sometimes marked 

 by its stronger convexity. The calyptra, which sur- 

 rounds the growing sporogonium like a delicate 

 envelope, is ruptured irregularly. 



2. The Andr eaeaceae * are small caespitose Mosses 

 with crowded leaves and numerous branches: the 

 shortly- stalked capsule, like that of Sphagnum, is 

 raised on a leafless pseudopodium above the peri- 

 chaetium. The rather long and pointed capsule 

 carries up the calyptra like a pointed cap, as in 

 the true Mosses, while the short seta remains con- 

 cealed in the vaginula. The tissue of the young 

 sporogonium is differentiated into a wall of several 

 layers of cells surrounding the single layer of the 

 spore-mother-cells without any intervening cavity, 

 and a central tissue, the columella ; the spore-producing layer has the shape of a bell 

 with its mouth downwards, as in the Sphagnaceae, and the columella terminates beneath 

 it. The mature capsule opens not by a lid, but by four lateral longitudinal slits, dividing 

 the capsule into four valves attached at top and bottom, which close in damp weather 

 and open in dry. 



3. The Phascaceae are little Mosses, whose short stem continues attached to the 

 protonema until the spores are ripe ; they may be regarded as the lowest forms of the 

 next group, the genus Phascum being intermediate between the two ; the distinguishing 

 mark of the group is that the capsule does not open by a lid, but releases the spores 

 only when disorganised by decay. While the genera Phasctim and Ephemerum 



FIG. .139. Sphagnum acitiifolium. A longitu- 

 dinal section of a bud-like envelope enclosing 

 female sexual organs ; ar archegonium, ch peri- 

 chaetial leaves still young, y the last leaves of the 

 bud-like envelope. B longitudinal section of the 

 sporogonium : sg the broad foot of which sg' is 

 fixed in the vaginula v, while the capsular part is 

 surrounded by the calyptra c, ar the neck of the 

 archegonium on the calyptra, ps the pseudopo- 

 dium. C Sphagnum sguarrosittn : the ripe 

 sporogonium sg with the lid d, and the ruptured 

 calyptra c, gs the elongated pseudopodium grow- 

 ing out from the perichaetium ch. After Schimper. 



1 Kiihn, Zur Entwicklungsgesch. d. Andreaeaceen, Leipzig, 1876 (Mittheilungen aus d. Ge- 

 sammtgebiet d. Bot. von Schenk u. Liirssen, I Bd.). 



