THE SIMPLER ORGANISMS 



67 



be seen something of the place algae occupy in the world, 

 something of their diversity of form and size, something 

 of their exquisite beauty and delicacy of organiza- 

 tion, and the principal differences between them in the 

 manner of their chlorophyl distribution. 



Study g. Observations on cell form and growth 



habit in algae. 



The materials needed are: i. A few of the larger, more 

 typical green algae (such asNostoc,Cladophora, Hydrodic- 

 tyon, Vaucheria and Chara) in water. 



Fig. 49. Some water-supply diatoms, i". Navicula; 

 / Cocconema; k, Asterionella; /, Tabellaria; m, 

 Fragilaria. ^ 



2. Some submerged or floating leaves of aquatic plants, 

 from which may be scraped a variety of diatoms and des- 

 mids. The student will get these for study by mounting 

 and examining the scrapings upon a slide. Stalked diatoms 

 may usually be found upon the filaments of the larger algae, 

 such as Cladophora. 



3. Strainings from the water tap, yielding diatom.s (fig. 

 49) and other algae that are common in the water-supply, 

 obtained by tying a sac of fine silk bolting cloth over the tap 

 and letting the water run slowly through for an hour or less. 



The study should consist in the examination by the stu- 

 dent of these different algae, one by one, observing and 

 recording the points outlined above. He will find it 

 desirable to familiarize himself somewhat with the princi- 



