166 A TEXT-BOOK OF BOTANY 



reproduction by producing sexual cells (gametes), which by 

 fusing in pairs (fertilization) form oospores. At first the 

 pairing gametes are alike, but later they become very 

 different, and are called sperms and eggs. The organ pro- 

 ducing sperms is called the antheridium, and that pro- 

 ducing an egg the oogonium; and among the Thallophytes 

 each of these organs consists of a single cell. 



(4) Algce the independent line. This means not only that 

 the Fungi have probably been derived from the Alga? by 

 losing the ability to make their own food, but also that the 

 higher plants have been derived from the Algae. Accord- 

 ingly the liverworts, about to be studied, are believed to 

 have developed from the Algae. 



91. General character of Liverworts. Liverworts are 

 found in a variety of conditions, some floating, many in 

 damp places, and many on the bark of trees. They seem 

 to be plants that have barely learned to live on land, and 

 this change from the water to the land is one of the greatest 

 and most important in the history of plants. Although in 

 general they are moisture-loving, some can endure great 



FIG. 160. Ricciocarpus: showing thallose body, forked branching, rhizoids on the 

 under surface, and spore-cases along the main axes (showing position of archegonia). 



dryness, so that the land habit can be said to have become 

 well-established among the liverworts. 



