(KD()(iONIUM 91 



82. Ulva, the sea lettuce. Follow in general the outline for Ulothrix, 

 noting the different morphology of the plant but similar structure of the 

 individual cells. Study especially the margins of the thallus where zoospores 

 may be developed. 



Reference. Principles^ Sec. 218. 



83. Cladophora. Follow an outline similar to that given for Ulothrix, 

 noting the different morpliology and very different cell structure. The 

 older cells contain many nuclei, i.e. are coenocytes, and have either a net- 

 like chromatophore with pyrenoids, or numerous somewhat irregular chlo- 

 roplasts. Permanent preparations in balsam stained with hsematoxylin 

 (Sec. 182) show these points well. 



84. Zoospores, their formation and habits. Use good material of 

 Ulothrix, Drajjanialdia, Stlgeoclo7umn, Ulva, or Cladophora. 

 Place considerable fresh material in a glass vessel brightly 

 illuminated on one side. 



A. Zoospores may be developed the next day, or perhaps a day 

 or so later. If formed, note : 



1. At what time they appear in greatest quantity as a green 

 cloud, and in which part of the vessel. 



2. Are they developed in the plant during the daytime ? 

 This will require the examination of material at various 

 times of day. 



3. Can the time of their escape from the plant be delayed 

 by keeping material in the dark ? 



B. A full study of the process of zoospore formation would 

 require the killing and preservation of material at intervals 

 during the night. 



85. (Edogonium.* * 



A. Observe the habit of the plant, the general morphology of 

 the filaments. Are they branched or unbranched ? Under 

 h.p. draw : 



1. The end of a filament and some cells in the middle region 

 crossed at one end by delicate lines, the caps. Note the 

 large chromatophore almost filling the cell. 



2. The remarkable disk-like holdfast developed by the basal 

 cell, especially well shown in younger plants. 



