88 PRACTICAL BOTANY. 



of cells that are intercalated in the filaments. Common 

 plants are Chcetophora and Cladophora. Cladophora, or 

 Water Flannel, is very common. It grows in running 

 water, forming long, dark-green stringy masses attached 

 to some fixed support at one end. It is made up of branch- 

 ing filaments, formed of elongated cylindrical cells, with 

 thick stratified walls. The branches develop from a sort 

 of bud formation near the top of the parent cell. As the 

 new branch forms, it becomes separated from the parent 

 cell by a partition wall that forms close to its base. The 

 cells are lined with protoplasm, and are also divided by 

 thin plates of protoplasm into a number of vacuoles. 1 



' 



& 



1 



FIG. 46. Sea Lettuce (Ulva). 



Another common plant, Sea Lettuce ( Ulva), is recog- 

 nized by its resemblance to the leaves of garden lettuce ; 

 it grows on the rocks and timbers in brackish and salt 

 water. 



1 Chsetophora, or Cladophora, affords good material for Practical 

 Studies. 



