240 



MORPHOLOG Y. 



The Horned Liverworts.* 



501. The horned liverworts take their name from the shape of the spo- 

 rogonium. This is long, slender, cylindrical, pointed, and very slightly 

 curved, suggesting the shape of a minute horn. Anthoceros is one of the 

 most common and widely distributed species. The plant grows on damp 

 soil or on rnud. 



Anthoceros. 



502. The gametophyte. The gametophyte is thalloid. It is thin, flat- 

 tened, green, irregularly ribbon-shaped and branched. It lies on the soil 



and is more or less crisped or 

 wavy, or curled, the edges nearly 

 plane, or somewhat irregular, 

 and with minute lobes, or 

 notches, especially near the 

 growing end. The general form 

 and branching can be seen in 

 fig. 279. Where the plants are 

 much crowded the thallus is more 

 irregular, and of ten. possesses nu- 

 merous small lateral branches in 

 addition to the main lobes. 

 Upon the under sid.e are the 

 slender rhizoids, which attach 

 to the soil. With a hand lens 

 there can be seen also upon the 

 under side small dark, rounded 

 and thickened spots, where an 

 alga (nostoc) is located. 



\ llli^ ^ If Sexual Organs of 



%fpH ^^%, | Anthoceros. 



502. The sexual organs of an- 



Fig. 279. 

 Anthoceros gracilis. A, 



thoceros differ considerably from 

 of the other liverworts 

 In the first place they 



several gameto- 



on which sporangia have developed, 

 , an enlarged sporogonium, showing its studied. 



elongated character and dehiscence by two . , . ,, .. 



'valves, leaving exposed the slender columella are immersed in the true tissue 

 on the surface of which are the spores, C, D, f th thallus, i.e., they do not 

 E, F, elaters of various forms, G, spores. < 



(After Scaiffner.) project above the surface. 



503. Antheridia. The antheridium arises from an internal cell of the 

 thallus, a cell just below the uppersurface. This cell develops usually a 



* May be used as an alternate study for marchantia. 



