SECT. I 



CRYPTOGAMS 



39:i 



portions of the opposite walls of a single layer of cells next to the operculum (Fig. 

 322), the teeth from portions of the external wall, and the cilia from portions of 

 the internal walls of the same layer. On the opening of the capsule the un- 

 thickened portions of this layer break away and the teeth and cilia split apart. 

 The transversely ribbed markings on their surface indicate the position of the 

 former transverse walls. 



The structure of the peristome varies greatly in different species of Bryinae. 



Fig. 321. — Mnium Tiornum. A, A plant with sporo- 

 gonium still bearing a calyptra (c) ; B, a plant with 

 ripe sporogonium ; s, seta ; 1c, capsule ; d, oper- 

 culum ; r/i, rhizoids ; C, mature capsule with 

 operculum (d) removed ; p, peristome ; D, two 

 peristome teeth of the outer row ; E, part of 

 inner peristome. (A, B, nat. size ; C x 3 ; D, E 

 X 5S.) 



Fig. 322. — Mnium Iwrniim. Transverse sec- 

 tion through the wall of the capsule in 

 the region of the ring ; a, cells of the 

 ring ; 1-4, successive cell layers with 

 the thickened masses of the inner and 

 outer peristome ; d', d", d'" , transverse 

 projecting ribs of the coalesced cilia c. 

 (X 240.) 



By its peculiar form and hygroscopic movements the peristome causes a gradual 

 dissemination of the spores from the capsule. 



The central axial portion of the capsule is occupied by the large-celled colu- 

 mella. It is completely surrounded by the sporogenous tissue, the so-called spore- 

 sac, which is separated from the wall of the capsule and sometimes also from the 

 columella by loose assimilatory tissue. Stomata occur in the epidermis of the 

 capsule. The Moss fruit, in conformity with its anatomical structure, takes part in 

 assimilation. It ripens slowly outside the archegonium, while the sporogonium 

 of the Liverworts remains enclosed within it until maturity. 



