106 PRACTICAL BOTANY. 



are called internodes. The stem also sends out branches 

 from the axils of the leaves at the nodes, and each branch 

 repeats the structure of the main stem. All the older 

 portions of the plants have the cell walls thickened by 

 deposits of carbonate of lime, which gives the plants their 

 common names, Stonewort and Brittlewort. The main 

 stem and each of the branches is tipped with an apical 

 bud, which is composed simply of the young cells that are 

 to develop into a new node and internode of the stem and 

 a new whorl of leaves. 



The sexual reproductive organs are borne on the leaves 

 on the upper part of the plant. They are just visible to 

 the naked eye. The antheridium is spherical in shape, 

 and is of an orange-red color ; it grows on the under side 

 of the base of a bract or leaflet. (Fig. 60, B.) The arche- 

 gonium is oval in shape, of a dark green, brown, or black 

 color, and grows in the axil of the bract or leaflet, just 

 above an antheridium. (Fig. 60, A.) Both are modified 

 leaves. In one species, Ohara crinita, the archegonium is 

 capable of germinating without having been fertilized by 

 the antherozoids, i.e., the plant is reproduced partheno- 

 genetically. 



No asexual reproduction by spores is known to exist in 

 any of the Characese. There is therefore no alternation 

 of generations. The plant is the gametophyte. A vege- 

 tive reproduction by means of branches which fall off 

 from the mother plant and grow into new plants occurs, 



THE CHARACE.E. PRACTICAL STUDIES. 



1. Detach an entire plant of Chara or Nitella from the 

 tangled mass in which it grows. Place it in a shallow dish 

 of water. Examine with a magnifying glass. Find the 

 rhizoids or rootlets. Do you find them at more than one 

 node ? Do you find them on the internodes ? Are they 



