KXAMINATION OP A LIVERWORT. 



195 



Pi-etty much as in the Mosses, though in Marchantia 

 the stalk of the capsule is very short, and the whole is 

 surrounded by a loose sheath 

 which grows up from the base 

 and at length completely encloses 

 it. The spores on germinating 

 develope into plant-bodies such 

 as we have described, so that the 

 alternation of generations is here 

 also well marked. 



344. Other Liverworts more 

 nearly resemble the Mosses in 

 form, having leafy -stems, from 

 the summit of wliich arise slender 

 stalks with capsules at the upper 

 end. These capsules, however, do 

 not open by a stoma, but are f our- 

 valved, and at maturity the valves 

 split asunder, allowing the escape of the spores. In the 

 leaves of these latter forms there are no veins of any kind. 

 Forms in which the plant-body is a flat expansion, as in 

 Marchantia, are distinguished as thalloid, while the leafy 

 forms are said to be foliose. 



345. It remains to be added that Marchantia'a.nA other 

 Liverworts reproduce themselves by buds as well as by 

 spores. ■ These buds (genimm) are formed in little cup- 

 shaped receptacles which appear on the upper surface of 

 the plant-body. They consist of simple masses of tissue, 

 which fall away when fully growh, and immediately 

 develope into new plants. 



.■?igr- 245. — ^Thallus with star-shaped receptacle bearing archegonia ; natural 

 Eize. (Thomg.) 



Fig. 245. 



