B. HEPATIC^ 

 MARCHANTIA POLYMORPHA, L. 



A. GENERAL EXTERNAL CHARACTERS 



I. Taking a fresh growing sod of Marchantia, observe the 

 following external characters with the naked eye or by help of 

 a pocket lens : 



1. The flattened form, sinuous margin, and prostrate position 

 of the branched, green thallus. 



2. Its dull, dark green upper surface, marked by diamond- 

 shaped areas, and in the middle of each of these a dot, which is 

 a single stoma. 



3. Projecting from the upper surface there are in most cases 

 small circular cups, with a finely crenate margin, in which may 

 be seen numerous dark green flattened bodies, the gemmae : 

 these may be easily detached by slight mechanical disturb- 

 ance. 



4. Note the organic apex of the thallus, situated at the base 

 of a terminal depression (compare the prothallus of Ferns) : 

 also that the branching is dichotomous, though the ultimate 

 development of the originally similar branches is unequal, so 

 that the result is a sympodium. 



5. In some cases the branches of the thallus may have 

 assumed peculiar forms, together with an erect position : these 

 are the branches which bear the sexual organs, and two 

 different types may be easily recognized as borne upon different 

 individual plants, viz. 



