468 LICHENES. [part n. 



ORDER CCXYII.— HEPATICE. 



These plants greatly resemble Mosses in their 

 appearance, but they differ in their construction. 

 The theca has no lid, but bursts into valves ; 

 and it generally contains not only sporules, but 

 tubes formed of curiously twisted threads, called 

 elaters. Jungermannia and Marchantia have a 

 calyptra, which the other genera are without ; 

 and in Jungermannia the theca has a sort of 

 sheath, which is sometimes called the calyx. 

 There are also stalked granules called anthers, 

 and warts which form on the leaves, and break 

 up into a kind of sporules. 



SUBCLASS 11.— APHYLLE^. 

 ORDER CCXVIII.— LICHENES. 



Though these plants are said to have no 

 leaves, they consist almost entirely of a kind 

 of leafy stem, called a frond or thallus, the 

 branches of which are called podetia (see a in 

 Jigs. 150, 151, and 152). The spores or sporules 

 are produced in what are called shields {h in 

 Jigs. 149, 150, and 151), which are generally 

 embedded in the thallus, and which, when they 



