336 



GENERAL MORPHOLOGY OF PLANTS 



highly developed organ than the egg case of the algae and fungi, 

 as will be seen in the study of examples. The fruit of the liver- 

 worts is a capsule containing spores, usually borne on a stalk. 



THALLOSE* LIVERWORTS. 



488. Marchantia. The thallose liverworts may be repre- 

 sented by a study of Marchantia. This plant grows on damp 

 soil, or rocks in swampy or moist, 

 shady places. The thallus is rather 

 broadly strap-shaped, notched at the 

 end, the growing point residing in the 

 notch. There is a " midrib " extend- 

 ing along the middle line. The plant 

 branches in a forked 

 manner, but often only 

 one of these branches con- 

 tinues its growth, 

 thus leaving pro- 

 jecting portions 

 on the sides of 

 the thallus. Ex- 

 amined with a 

 hand lens the 

 upper surface is 



seen to be marked off into regular rhomboidal areas, and in the 

 center of each is a stomate opening (fig. 293). These open into 

 quite large chambers in which most of the chlorophyll-bearing 

 tissue is in the form of short, upright chains of cells. This 

 tissue, with the epidermis, belongs to the upper layer of the 

 thallus. The lower layer lacks chlorophyll, containing some 

 cells with spiral thickenings and bearing the rhizoids. There 

 are numerous slender rhizoids on the under surface, some of 

 which have numerous thickenings on the inside of the wall. 

 There are also thin membranous scales on the under surface 



Fig. 294. 

 Male plant of Marchantia bearing antheridiophores. 



* Those liverworts in which the plant body is a true thallus. 



