360 PRACTICAL BOTANY 



B. HEPATIOE 

 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 pros* 

 trate 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 (see below). 



3. Projecting from the upper surface may also be 

 seen 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 disturbance. 



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 



