176 THALLOPHYTES 



of many millions of dollars every year. This loss is so enormous 

 that a new branch of botany, known as plant pathology, has 

 been developed for the study of plant diseases and methods for 

 their control. 



EXERCISES WITH THALLOPHYTES 



1. Examine algae, as many as circumstances will permit, and note the 

 points referred to in the text. The algae may be collected from small 

 streams and kept in jars and dishes on the laboratory tables for many 

 days and studied with the aid of the compound microscope. 



2. Collect many specimens of parasitic fungi found on leaves 

 and fruits of plants, especially on cultivated plants. Study them in their 

 different stages of reproduction. 



3. Develop yeast in a weak solution of water and sugar and study 

 specimens under the microscope. 



4. Keep some moistened bread in a warm chamber (i. e., under an 

 inverted jar or in a closed dish). When mould has developed study its 

 different stages. 



5. Keep some dead flies in an open bottle of water and watch for 

 the development of Saprolegnia; then make a microscopic study of it. 



QUESTIONS 



1. What three groups are included in the Thallophytes ? 



2. In what respect do all the algae resemble each other? 



3. Describe reproduction in unicellular algae. 



4. Describe reproduction in Spirogyra. 



5. Describe reproduction in Ulothrix. 



6. Describe the forms of reproduction in Oedogonium. 



7. How is reproduction accomplished, in Vaucheria? 



8. Tell of the economic value of algae. 

 0. How do the fungi differ from algae? 



10. Describe the structure of yeast plants. 



11.' What is the structure of bread mould? Tell of its reproduction. 



12. Give examples of parasitic fungi. Of what importance are they? 



13. Tell what you can of the fleshy fungi. 



Reference. Read accounts of algae and of fungi, found in an encyclo- 

 pedia and special books on these subjects. 



