368 



ORGANOGRAPHY, 



Fig. 805. Fig. 806. Fig. 807. 



i 



Tig. 804. Coscinodonpulvinatiis. sp. Sporangium enclosed in the calyptra. 



t. Seta or stalk, v. Vaginule. From Henfrey. Fig. 805. The Hygro- 



metric Cord-Moss {Funaria hygrometrica). f. PerichEetial leaves, p. 

 Stalks or setm. each of which supports a sporangium, «, covered by a 



calyptra, c. Fig. 806. Sporangium of the Extinguisher-Moss (Encahjpta 



vulgaris) before dehiscence, u. Sporangium, covered by a transparent 

 calyptra, c, and supported on a seta, k. Beneath the calyptra is seen 



the lid or operculum, o. Fig. 807. Tiie sporangium, «, of 806 after 



dehiscence. The calyptra and operculum, o, being removed, the 

 peristome, p, may be seen. 



tween this axis and the walls of the sporangium is filled with 

 free spores, which are small cells with two coats and markings 

 resembling those of pollen-cells. The sporangium is either in- 

 dehiscent ; or it opens by four vertical slits so as to form four 

 valves ; or more commonly by a transverse slit close to the apex 

 like the transverse dehiscence of fruits, by which a kind of lid is 

 formed, called the operculum {figs. 807, o, and 808) ; this lid is 

 either persistent or deciduous. The sporangium is sometimes 

 much dilated at the base, where it joins the seta ; this swelling 

 is called an apophysis, or, if it only occurs on one side, a 

 struma. 



The wall of the sporangium is commonly described as con- 

 sisting of three cellular layers, the outer of which forms the 

 operculum, and the inner two layers the peristomium. At the 

 dehiscence of the sporangium the siovia or mouth is entire, smooth, 

 or unfurnished with any processes {fig. 808) ; or it is surrounded 

 by one or two fringes of teeth, called collectively the peristome, 

 which are formed from the two inner layers of the wall of the spo- 

 rangium {fig. 807, p'). These teeth are always four or some multiple 

 of that number. Sometimes a membrane from the inner wall is 



