262 



PEACTICAL BOTANY 



the stem upon which the archegonium grew. This gives the 

 lower end a foothold in the stem, and by reason of its close 



contact this end, or foot as it is 

 called, absorbs food material from 

 the stem. The young stalk also 

 bears chlorophyll and may manu- 

 facture some of its own food. The 

 upward end elongates rapidly and 

 carries up with it the old arche- 

 gonium wall, which meantime has 

 grown somewhat (Figs. 216 and 

 219). This elongated structure 

 is called the seta, which means a 

 " bristle " or " hair." Since this old 

 archegonium now changed is like 

 a hood, it is called calyptra, which 

 means " hood." Beneath the calyp- 

 tra, at the end of the seta, there 

 is formed the enlarged capsule. 

 Within the capsule, by division 

 of certain specialized cells, large 

 numbers of spores are formed. At 

 the extreme tip of the capsule, 

 beneath the calyptra, is the mouth, 

 or peristome, which is covered by a 

 lid known as the operculum, mean- 

 ing the "cover" or "lid." When 

 the spores are ripe the calyptra 

 may fall off and the operculum be 

 thrown off by swelling of the cells 

 immediately below it. There then 

 appears around the margin of the 

 mouth a row of teeth (Fig. 220). 

 The number of teeth in a capsule 

 is definite for each species of moss, 

 and sometimes special students of 



FIG. 219. Growth of the moss 

 oospore to form the sporophyte 



At A is a diagram of the oospore 

 after it has gone through several 

 cell divisions and has spread the 

 archegonium wall. B shows the 

 tip of a plant stem with parts of 

 leaves about. The oospore has 

 grown into a stem-like structure 

 (s), has its lower end inserted in 

 the old plant stem (g), and the 

 other end has carried up the en- 

 larged archegonium wall (a) as 

 the hood or calyptra. After Sachs 



