266 



ESSENTIALS OF BOTANT 



MARCHANTIA, ONE OF THE LIVERWORTS 



342. Occurrence. — Marchantia polymorpha,^ the com- 

 monest species of the genus, is widely distributed in this 

 country and in Europe. It is found on damp soil or rocks, 



especially in shaded places. 



343. Gross structure. — Secure 

 if possible specimens in the fruit- 

 ing condition (Figs. 190, 191).2 

 Examine with and without the 

 magnifying glass and note : 



(a) The size, shape, and color 

 of the thallus or body of the plant. 

 (p) The mode of forking. 

 Branches are formed in pairs on 

 each side of the growing tip. Do 

 they develop equally? 



(c) The distinctions between 

 the upper and the lower surface 

 of the thallus. Look for scales 

 on either surface and for rhizoids 

 or root-like organs. Examine the 

 upper surface with the magnify- 

 ing glass and draw a portion of it, showing the diamond-shaped areas, 

 each with a pore in its center. 



(rf) The buds, or organs of vegetative reproduction, small struc- 

 tures which, when detached, serve to produce new plants. 



(e) The male receptacles, stalked disks with scalloped margins. 



1 If ilnrchantia cannot be easily obtained, Lunularia, a genus very com- 

 mon in greenhouses, may be substituted. It is easily recognized by the cres- 

 cent-shaped cups in which the reproductive buds are borne. The structure _ 

 is rather similar to that of Marchantia and the mode of vegetative reproduc- 

 tion is the same in botli. Lunularia as found in our greenhouses does not 

 undergo sexual reproduction. 



2 M. diyuncta, which is shown in these figures, differs considerably in the 

 form of the receptacles from M. polymorpha. The male receptacle of the 

 latter looks a good deal like tlie female receptacle of the former but is much 

 shorter-stalked. 



Fig. 189. Vertical Section through 

 a Lobe of Ricciocarpus. (Magni- 

 fied.) 



ti,antheridium; e, epidermis; i, spongy 

 interior of thallus with air-chambers ; 

 /■, bases of rhizoids. 



