HORNED LIVERWORTS 



343 



the stem. The plant clings very closely to the bark of the 



tree which aids in retaining moisture. In addition each of these 



leaves has a lobe on the under side (next the tree) 



which is sac -like and holds water. This water is doled 



out to the plant during dry periods. It remains so 



long in these pockets that minute animals belonging 



to the crustacean group make it their home. In Cali- 



fornia one of the liverworts growing on the ground 



forms subterranean tubers which tide the plant over 



the dry season. 



494. The capsule (sporogonium) of the leafy- 

 stemmed liverwort. This is a stalked capsule, and 

 the capsule splits down to the base into four valves. 

 In some species elaters are mixed with the spores. 



HORNED LIVERWORTS (ANTHOCEROTES). 



Fig. 305- 



foliose liver- 



495. The horned liverworts. The horned liver- 

 worts may be represented by Anthoceros. It grows in 

 wet, muddy places. The thallus is thin, dark green, 

 and irregularly branched and overlapping (fig. 306). 

 The sexual organs are immersed in the thallus, the sperm cases 

 in groups in a cavity, while the wall of the immersed egg case 

 is united with adjacent cells of the thallus. The capsule is 

 long, slender and slightly curved, its form suggesting the 

 name of " horned " liverworts. Its base is surrounded by a 

 slender, short outgrowth of the thallus. The growing point 

 of the capsule is near the base, the older portions being con- 

 stantly raised by growth at the base. The capsule consists of 

 a wall and a column of sterile tissue, between which is a 

 layer of spore-bearing tissue in the form of a tube. Some of 

 the cells of this spore-bearing tissue are mother cells of spores, 

 each mother cell forming four spores. Other cells alternating 

 with them form short, spirally marked elaters. From the 

 nature of its growth the spores at the apex are older than 

 those below. The capsule at maturity splits longitudinally and the 



