INTKODUCTORY 



General Characters. The Hepatic^ include quite di- 

 verse forms of vegetation, judging from the outward habit of 

 the plants composing the group, yet all are more or less inti- 

 mately related in their essential, that is. their reproductive 

 characters. The lower forms consist of a mere expansion of 

 tissue with no differentiation of stem and leaves. These thal- 

 loid forms are quite frequently confused with certain forms of 

 lichens, but can be easily distinguished by the fact that while 

 the lichen is usually rather dry and crustaceous or leathery, 

 the hepatic is more loosely cellular or spongy in texture, and 

 presents a moist or somewhat juicy appearance under pressure. 

 Some of the aquatic forms have also been mistaken for algae. 

 The higher forms of Hepaticae are more moss-like in general 

 appearance, consisting of a stem and leaves usually closely 

 creeping over some substance, which may be the ground itself, 

 rotten wood, living trees, or rocks. These higher forms are 

 sometimes confused with the true mosses (Musci), but can 

 usually be distinguished by having the leaves two-ranked, while 

 the mosses proper have them in several or many ranks. The 

 more technical differences will be made apparent at a later 

 paragraph. 



Habits of Growth. The Hepaticse are as various in 

 their habits of growth as they are diverse in their external ap- 

 pearance. They may be looked for in almost any situation, 

 though certain conditions seem most favorable for continued 

 and thrifty growth. Some may be found on the ground in 

 ditches or in moist places, others grow on rocks or stones by 

 brooks or rivulets, while others still are found on rotten logs 

 or stumps in forest or swamp. Some species are found among 

 other mosses, notablv the SplxupKi of swam|)s and ])eat-bogs. 



