SELECTED NOTES. 279 



fruit is ripe, and is itself covered with another vestment called the 

 " calyptra" (the origin of which will be described in another place), 

 which is so strongly developed in some species of this family. 

 When the fruit is ripe, the first part, as a rule, to disappear is the 

 calyptra, then the operculum, which discloses to view a beautiful 

 arrangement of teeth fringing the mouth of the spore case, and 

 which is known as the " peristome." These teeth are all united 

 to a membrane known as the " epiphragm," or " tympanum," 

 which serves as a protection to the interior of the spore case after 

 the dehiscence of the operculum. It will thus be seen that the 

 fructification of the lowly moss is a ver) complicated arrangement. 



The objects represented in Fig. i are all from Atrichiim 

 undulatu77i^ or, as it is sometimes called, Cathannea undulata. 

 At / is shown the fully developed capsule, from which however 

 the calyptra, ^, has fallen, showing the long pointed operculum still 

 adherent. Detached opercula may be seen at h and /, while at g 

 andy are shown two capsules from which the opercula have fallen, 

 giving a side view of the previously enclosed peristome. At d 

 and e are two examples of the peristome and the epiphragm 

 enclosed. There are thirty-two of these peristomal teeth in the 

 species under consideration, but in some members of the family 

 they number sixty-four, as in Polytrichutn juniperinmn. Occasion- 

 ally they may be seen united in pairs. 



The tympanum, or epiphragm, is one of the distinguishing 

 features of the family, and has special structural modifications, 

 according to the species. The caliptra, ^, is not a salient feature 

 in this species, but it is a very striking object in some, as in P. 

 urfiigerufH, the calyptra of which is seen at Fig. 3. 



Fig. 2 shows the same organ from P. ju7iiperinum^ and Fig. 5 

 is from P. pilifermn. It will thus be seen that the calyptra is a 

 very variable organ, even in members of the same family, and is 

 a great help in the determination of species, a and b (Fig. i) 

 are two halves of the same capsule ; in b may be seen the 

 columella in the centre of the chamber ; it is from differentiated 

 cells of this organ that the si)ores take origin. The columella of 

 this species when in the living state is cylindrical, but in some 

 species, as in P. abides^ it is four-winged, as may be seen by 

 reference to Fig. 4. 



