MOSSES FERNS 



19] 



and protect the young growing capsule. It is finally torn loose and 

 carried up on the spore-case. The mouth of the capsule is closed by 

 a circular lid, the operculum, having a conical projection at the center. 

 The operculum soon drops, or it maybe removed, displaying a fringe 

 of sixty-four teeth guarding the mouth of the capsule. 



This ring of teeth is known as the peristome. Iu most mosses 

 the teeth exhibit peculiar hygroscopic movements, i. e., when moisl 

 they bend outwards and upon drying curve in toward the mouth of 

 the capsule. This motion, it will be seen, serves to disperse the 

 spores gradually over a long period of time. 



Not the entire capsule is filled with spores. There are no elaters, 

 but the center of the capsule is occupied by a columnar strand of tis- 

 sue, the columella, which expands at the mouth into a thin, mem- 

 branous disk, closing the entire mouth of the capsule excepl the 

 narrow annular chink guarded by the teeth. Iu this 

 moss the points of the teeth are attached to the margin 

 of the membrane, allowing the spores to sift oul through 

 the spaces between them. 



When the spores germinate they form a green, 

 branched thread, the protonema. This gives rise directly 

 tn mi i" plants, which appear as little I mi Is on the threads 

 When the moss plants have sent their little rhizoids into 

 the earth, the protonema dies, for it is no Longer neces- 

 sary for thi> support of the little plants. 



V. 



\ 



I'l'.KNS 



The adder's tongue fern, Ophioglossum vulgatum, 

 shown in Fig. ''< I 1 , is one of a peculiar type of ferns be- 

 longing to the family Ophioglossacero. This plant ha- a 

 short, subterranean Btem from which e Bingle frond un- 

 folds each year, The roots arise near the bases of the 

 leaves. The leaves are curiously divided into a Bterile 

 and a fertile part, the latter being a Bporophyll. The 

 sterile pari has a tongue-shaped blade which is narrowed 

 Id a petiole. The young haves are inclosed by the Ophiogloiaam 

 Bheathing base of the petiole. The growth is very rolgutum. 

 slow, so that it takes Beveral years for each leaf to develop before it 

 i-. ready to unfold. During its development each leaf is Bheathed bj 

 t he one preceding it . 



The sporophyll is elevated on a stalk arising near the base of the 

 sterile part of the frond. The upper pari consists of a spike hearing 



