THE PLANT GKOUPS 83 



sexually ? If so, trace out the stages of reproduction 

 found in your material. 



4. Sketch the different species of algse observed and show 

 stages in reproduction where such are observed. 



FUCUS VESICULOSUS (MARINE ALGA) 



1. Habitat and habit. 



a. Is the water habitat of Fucus more or less stable and 

 permanent than that of fresh-water algse ? Do you 

 know of fresh-water forms which attain to the size 

 or the structural differentiation of Fucus ? Is there 

 a reason, based on difference of habitat, for this 

 difference in habit between Fucus and fresh-water 

 species ? Note the differentiation of the plant body into 

 root and shoot portions. What is the function of the 

 root and shoot? How is each part adapted to its 

 special function ? How is it adapted to photosyn- 

 thesis ? to resistance to waves and water currents ? to 

 protection from dessication, or drying, when exposed 

 at low tide ? 



I. Study the form and branching of Fucus. Can you de- 

 termine how the very regular mode of branching 

 occurs ? Where are the growing points ? Is there any- 

 thing like a bud ? Observe the swollen floats which 

 buoy the plant up in water. 



c. Sketch a portion of a Fucus plant to show its habit and 

 mode of branching. 



2. Microscopic structure. Examine thin sections cut across 



a FufMS plant. What is its general structure ? Is there 

 an outer protective epidermis ? Where is the chlorophyll 

 layer or layers? Does the chlorophyll-bearing layer 

 look green? Explain the color of this layer. What 

 kind of tissue occupies the center of the branch as 



