XVIII. CRYPTOGAMS 

 Introductory Note 



The following Experiments on a few typical seedless plants 

 are added for the purpose of giving the student a general 

 idea of what is meant by the so-called flowerless plants. 

 Most of these Experiments are such as may be undertaken 

 without the aid of a compound microscope. The unaided eye 

 is able in most cases to see the structures alluded to, and a 

 simple magnifier is all that will be required. 



As every well-equipped school is provided with at least 

 one compound microscope, the use of the latter is recom- 

 mended. 



198. ALGAE (pond scum) 



Pond scum (spirogyra) is one of the commonest water 

 plants, where it often abounds in still or slow-flowing 

 streams. It is easily recognized by its bright green, silky 

 threads, which form dense tangles. At times they throw 

 off great masses of gas which gives them a frothy appearance, 

 hence it is often 'called " frog spittle." 



Object. To study growing algae. 



Method. Place a mass of pond scum in a tall beaker 

 (a) or preparation jar and set it in the strong sunlight. 



Place another (6) similar mass in darkness or diffused 

 light. After one hour place the jars side by side and com- 

 pare their contents. Where is the green alga in (a) ? In 

 (6)? Do you discover any reason for this? Change the 

 bottles, placing (a) in shade and (6) in strong sunshine for 



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