324 BOTANY: PRINCIPLES AND PROBLEMS 



759. What are the advantages of the system of air chambers in the 

 thallus of the Marchantiales? 



760. Enumerate the various ways in which the Anthocerotales are 

 closer to the higher plants than are the rest of the bryophytes. 



761. Name all the ways you can think of in which the sporophyte of 

 Anthoceros resembles, and differs from, that of the seed plants. 



762. The shoots of Sphagnum are greenish or grayish-green instead 

 of dark green as in most mosses. Why? 



763. Why is sphagnum (the dead and dried remains of Sphagnum 

 plants) a very good absorbent? 



764. What important part in the economy of nature is played by 

 the mosses? 



765. What does a moss protonema resemble, and what does its i)res- 

 ence suggest as to the ancestry of the mosses? 



766. Bryophytes are generally very tolerant of shade. Explain. 



767. Where at present on the earth is vegetation "headed by a 

 vanguard of mosses"? 



768. From your study of the bryophytes (and of other plant groups) 

 do you think that all parts of the plant change at the same rate during 

 the progress of evolution? Explain and illustrate. 



REFERENCE PROBLEMS 



130. Where does peat come from and how has it been formed? 



131. Why is sphagnum so much used for surgical dressings? 



132. Give the derivation of the following terms and explain in what way 

 each is appropriate: 



Archegonium Columella Hypophysis 



Elater Operculum Protonema 



Calyptra 



