166 A TEXT-BOOKk OF BOTANY 
reproduction by producing sexual cells (gametes), which by 
fusing in pairs (fertilization) form odspores. 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) Algu the independent line.—This means not only that 
the Fungi have probably been derived from the Alge by 
losing the ability to make their own food, but also that the 
higher plants have been derived from the Algze. Accord- 
ingly the liverworts, about to be studied, are believed to 
have developed from the Alge. 
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 
Fic. 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. 
