INTRODUCTION 3 



Cyanophj^ceae, Schizomyoetes, M^^\omycetes, Bacillariophyceae, and 

 possibly some of the flagellate groups. The remaining classes of algae 

 might then be retained in one division and the remaining classes of fungi 

 in another, or some or all of these classes might be raised to the rank of 

 divisions. Much difference of opinion exists as to which classes should be 

 placed together. 



Two different arrangements for classifying the thallophytes are as 

 follows : 



3. Basidiomycetes 



' Several other classes, consisting almost entirely of flagellates, are generally recog- 

 nized. These are the Euglenophyceae, Chrysophyceae, Cryptophyceae, and 

 Dinophyceae. 



The elevation of a great number of classes to the rank of divisions, thus 

 making each coordinate with the bryophytes, pteridophytes, and sperma- 

 tophytes (or even with the tracheophytes, if the last two are combined), 

 tends to conceal relationships and gives a prominent place to small, 

 obscure groups. Moreover, when the names of all the divisions are 

 given the termination phyta, in order to make them consistent through- 

 out the plant kingdom, many lose their distinctive meanings, and we find 

 the various groups of algae called Chlorophyta (green plants), Phaeophyta 

 (brown plants), Rhodophyta (red plants), etc. 



Classification of Embryophyta. The position of the Bryophyta 

 as a division of the plant kingdom seems secure. Those botanists 

 who classify the higher plants on the basis of vascular anatomy discard 

 the names Pteridophyta and Spermatophyta and designate all vascular 

 plants as Tracheophyta. They point out that a marked tendency 

 toward seed formation was present in several extinct groups of pterido- 

 phytes, and that the most primitive group of seed plants, the extinct 

 Cycadofilicales, were very fern-like. The Tracheophyta, constituting a 

 division, are separated into four classes, the Psilopsida, Lycopsida, 



