Simple Plants With Chlorophyll — Algae 165 



carpogonia (kar po -go' ni a) (Gr. karpos, fruit; gonos, birth). Each 

 carpogonium has an elongated trichogyne (trik'ojin) (Gr. thrix, hair; 

 gyne, female) to receive the nonmotile sperm brought by the water. The 

 nucleus of the sperm travels down the trichogyne to the carpogonium, 

 where nuclear fusions and cell divisions occur. Eventually this results 

 in the formation of many filaments, the tips of which produce many 

 carpospores. Other filaments form an urn-shaped covering which en- 

 closes the carpospores. When the latter are released through an opening 

 in the covering, they produce new plants which form sporangia (spor- 

 an' ji a) (Gr. sporos, spore; angos, vessel), each with four tetraspores 

 (tet'raspor) (Gr. tetras, four; sporos, spore). The sporangia are borne 

 on the central core cells just beneath the jacket cells. When liberated, 

 the tetraspores produce Polysiphonia plants, either with male antheridia 

 or with female carpogonia. This complex life cycle consists of ( 1 ) male 

 or female plants, (2) the zygote and its carpospores, and (3) plants pro- 

 ducing tetraspores. None of the reproductive cells are motile which is 

 characteristic of red algae. 



QUESTIONS AND TOPICS 



1. List the general characteristics of the thallophytes (Subkingdom Thallophyta). 



2. List the distinguishing characteristics by means of which the following phyla 

 may be differentiated: Cyanophyta, Chlorophyta, Chrysophyta, Phaeophyta, 

 and Rhodophyta. 



3. In what ways do algae differ from the fungi? 



4. List all the asexual methods of reproduction found in the algae, describing 

 each. 



5. List all the sexual methods of reproduction found in the algae, describing 

 each. 



6. Explain what is meant by metagenesis (alternation of generations). Describe 

 what is meant by a gametophyte. Explain what is meant by a sporophyte. 



7. What evidence from your studies of algae can you give for an explanation 

 for the origin of sex? 



8. Describe the increase in complexity of structures and methods of reproduction 

 as you progress from the simpler to the higher types of algae. 



9. What progressive developments take place in the vegetative body of the algae 

 as we go from the simpler to the higher types? 



10. List the evolutionary changes which take place in individual cells of algae 

 as we go from the simpler to the higher types. 



11. List the economic importance of the algae of each phylum, Including bene- 

 ficial as well as harmful items. 



12. Make a list of the habitats for each phylum to which the algae belong. 



13. Explain the importance of algae in the lives of fish and other types of aquatic 

 organisms. 



