Key to the Tribes 



Crown of oogonium composed of 5 cells; oogonium always above 



the antheridium ( in monoecious species ) Chareae 



Crown of oogonium composed of 10 cells (5 pairs, 2 cut off from 

 the tip of the cortical cells of the oogonium); oogonium below 

 or beside the antheridium; stem uncorticated Nitelleae 



Tribe Nitelleae 



In this tribe the stem bears whorls of short branches and 2 or 

 more branches of indefinite growth. The plan of branching is dicho- 

 tomous or trichotomous, and in many forms the secondary branches 

 or 'leaves' all terminate at about the same level and are usually less 

 than the internodes in length so that (especially in some species of 

 Nitella) a beaded appearance results. The plants are entirely un- 

 corticated and in most forms (particularly Nitella) they are limp 

 and flexible. The coronula ('crown') of the oogonium is composed 

 of 10 cells in 2 tiers at the ends of the 5 corticating cells of the 

 female organ. The antheridium may be vertical at the end of a 

 short stalk from the node of a fertile branchlet, or lateral ( Tolypella ) 

 and either sessile or stalked. In the monoecious species the oogonia 

 are below the antheridia (Nitella) or above and beside them 

 ( Tolypella ) . 



Key to the Genera 



Branching regular and symmetrical; antheridia terminal and 



vertical on a branchlet in the furcations; 



oogonia below the antheridia Nitella 



Branching irregular or not symmetrical, some branches longer 



and giving a scraggly appearance; antheridia lateral in the 



furcations; oogonia beside the antheridia or 



appearing to be above them Tolypella 



NITELLA (C. A. Agardh) Leonhardi 1863, p. 69 



Branches of unlimited growth, usually 2 at each node, the sex- 

 organ-bearing branches repeatedly forked and terminating at the 

 same level; antheridia terminal on a short stalk among the furcations 

 of the branchlets; oogonia lateral, either just below an antheridium, 

 or solitary on the node of a 'leaf.' 



Key to the Species 



1. Plants small, 2-5-(8) cm. tall; ultimate divisions 



of the branchlets (rays) 2-celled 2 



1. Plants larger; ultimate divisions of the branchlets 1-celled 3 



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