138 Aquatic Organisms 



They grow attached to the soil. They grow to consider- 

 able size, often a foot or more in length of stem. They 

 grow by apical buds, and they send out branches in 

 regular whorls, which branch and branch again, giving 

 the plant as a whole a bushy form. The perfect regu- 

 larity of the whorled branches and the brilliant colora- 

 tion of the little spermaries borne thereon, doubtless 

 have suggested the German name for them of "Cande- 

 labra plants." 



The stone worts are so unique in structure and in repro- 

 ductive parts that they are easily distinguished from 

 other plants. The stems are made up of nodes and 

 internodes. The nodes are made up of short cells from 

 which the branches arise. The internodes are made up 

 of long cells (sometimes an inch or more long), the 

 central one of which reaches from one node to another. 

 In Nitella there is a single naked internodal cell com- 

 posing entirely that portion of the stem. In Chara this 

 axial cell is covered externally by a single layer of 

 slenderer cortical cells wound spirally about the central 

 one. A glance with a pocket lens will determine whether 

 there is a cortical layer covering the axial internodal 

 cell, and so will distinguish Chara from Nitella. Chara 

 is usually much more heavily incrusted with lime in our 

 commoner species, and in one very common one, Chara 

 fcetida, exhales a bad odor of sulphurous compounds. 



The sex organs are borne at the bases of branchlets. 

 There is a single egg in each ovary, charged with a rich 

 store of food products, and covered by a spirally wound 

 cortical layer of protecting cells. These, when the egg 

 is fertilized form a hard shell which, like the coats of a 

 seed, resist unfavorable influences for a long time. 

 This fruit ripens and falls from the stem. It drifts 

 about over the bottom, and later it germinates. 



At the apex of the ovary is a little crown of cells, 

 between which lies the passageway for the entrance of 



