THE CHAROPHYTA 



387 



From the root-node cell a number of rhizoids are formed which supple- 

 ment the primarj^ rhizoid formed by the first division of the germinating 

 oospore. The internodal cell elongates and carries up the stem-node cell, 

 above which the protonema terminates in a short row of cells. The stem- 

 node cuts off in sequence a ring of peripheral cells. From these a whorl of 

 lateral filaments of very limited growth is formed, with the exception of the 

 oldest of the peripheral cells, which cuts off an apical cell, which then divides 

 to form the segments of a new sexual plant. Thus the sexual plant arises 

 as a lateral bud of the protonema in a way not unlike what we have already 

 described in Batrac/iospertnuni, and resembling the process we shall see 

 later in the Bryophyta, though it must be clearly realised that there is no 

 homology between the structures in the two cases. 



Vegetative Propagation 



At almost any stage in the life of Chara vegetative propagation can 

 occur. Secondary protonemata may develop even more rapidly than primary 

 ones. Fragments of nodes, dormant cells of plants after hibernation or 

 the basal nodes of primary rhizoids may all produce these secondary pro- 

 tonemata, from which fresh sexual plants can arise. It is probably this power 

 of vegetative propagation which explains the fact that species of Chara are 

 generally found forming dense mats in the beds of ponds or streams, covering 

 quite large areas. 



It will be seen that very little comparison can be made between this and 

 any other group of plants. That the Characeae are highly specialized is 

 obvious, yet it is noteworthy that a fundamentally simple system of cellular 

 nodes and internodes has been modified and adapted to serve very varied 

 purposes in a striking and unique manner. 



The life-cycle of Chara may be graphically represented by Fig. 371. 



Oospore 



Antherozoid Oosphere 



\ 



Protonema 



I 



Antheridium Oogonium 



Chara Plant 

 Fig. 371. — Life-cycle oi Chara. 



