PREFACE 



Tins shall volume on the simple, holocarpic, bi- 

 flagellate Phycomycetes is the second in a series of 

 lectures presented to graduate and research stu- 

 dents o£ mycology at Columbia University on the 

 origin, development, phytogeny, and evolution of the 

 lower organisms. These simple Phycomycetes, with 

 the exception of the Lagenidiaceae, were formerly 

 included in tin- Chytridiales by most mycologists, 

 hut with the recognition in recent decades that the 

 Dumber, position, and relative lengths of the flagella 

 are of fundamental phylogenetic significance, the 

 viewpoint has gradually developed that these species 

 cannot be incorporated in the same order with the 

 posteriorly uniflagellate chytrids. On the basis of 



present-day evidence, the author concurs with this 



belief and is accordingly presenting these biflagel- 



late species apart from the chytrids. Many of these 

 simple fungi exhibit distinct oomycetous characters 

 and tendencies and should perhaps be included di- 

 rectly in existing or new families of the Phycomy- 

 cetes, while the life cycles of other species suggest 

 .1 relationship or at least a parallelism in develop- 

 ment with the Plasmodiophorales and Proteomyxa. 

 It is thus impossible at present to include all of them 

 in one family or order and very difficult to assign 

 them to a definite position in a natural system of 

 classification. For this reason they are treated sepa- 

 rately and are referred to here as a heterogeneous 

 collection of simple, holocarpic. biflagellate Phyco- 

 niyeetes. This long title is obviously inadequate and 

 can also be extended to include other Phycomycetes 

 not discussed here, the tballi of which may some- 

 times be holocarpic. A more adequate and briefer 

 title is not available, although the descriptive name 



Holobiflagellomycetes is suggested. The use of the 

 term "simple" is not to be interpreted as meaning 

 th.it these fungi ;ire primitive and have given rise 

 directly to the higher Oomycetes and Zygomycetes. 



Nor does the author wish to convey the impression 

 that by discussing these diverse fungi under one title 

 that In- considers them as constituting a natural phy- 

 logenetic series. Whether or not they comprise sev- 

 eral distinct families is obviously open to question. 



The family Wbroninaceae, for example, includes 



several dissimilar genera and is very doubtful. 

 Should the type species Woroni na polycystis prove 



to be a member of tin- Plasmodiophorales. as set ins 



quite likely at present, tin former family name 

 would no longer be tenable. The author has none- 

 theless grouped the genera in five families, realiz- 

 ing fully that the grounds for doing so are woefully 

 inadequate. Mycologists will doubtless disagree with 



this arrangement, but in our state of meager knowl- 

 edge concerning many of the genera and species, 

 classification into families is not SO important at 



present, in the author's opinion, as making available 

 to research students all known facts and data. 



These fungi have been the subject of study for al- 

 most a century, but no serious attempt has been made 

 to summarize the widely scattered data in zoological 

 and botanical journals. Fischer ('92), Schroeter 

 ('97), and Mindcn ('11) discussed rather fully the 

 species known at the turn of the century, but since 



that time most textbooks of mycology have given 

 scant attention to them. During the past two dec- 

 ades several new genera and species have been dis- 

 covered, and additional intensive studies on long 

 known species have modified our concepts of host 

 range, sexuality, relationships, etc., within the 

 group. In light of these discoveries and the fact that 

 these simple holocarpic fungi are so significant from 

 the standpoints of phylogeny and evolution of flu- 

 higher Phycomycetes. the author believes that a 

 separate and complete treatment of them is very es- 

 sential and worthwhile, particularly in stimulating 

 research. A full discussion of the doubtful and ex- 

 eluded species is also presented with the purpose of 

 making these data available to researcli workers. 

 Although the author agrees with the view that Ach- 

 lyogeton, so far as it is now known, should be ex- 

 eluded because of its reported posteriorly uniflagel- 

 late zoospores, he nevertheless believes it may pos- 

 sibly prove to be a valid member of the group. 



In the text which follows very few technical 

 terms are used. A glossary is accordingly unneces- 

 sary and has been omitted. Separate bibliographies 

 are provided at the end of each chapter to expedite 

 reference to the literature on particular subjects, 

 genera, and species. A host index of plant and ani- 

 mal genera and species, together with an inclusive 

 bibliography, is presented in the final chapter. Due 

 to war conditions, many of the recent European and 

 Asiatic journals have not been available, so that this 



index and bibliography may not be complete. The 



illustrations of numerous authors in America and 

 other parts of the world have been freely used by 

 the author. Grateful thanks for this courtesy is here- 

 by expressed to them. These contributors are too 

 numerous for individual mention, but full credit for 

 their drawings is given in the descriptions of the 



plates. 



Columbia University 

 Ni:w Yobs t !m 

 October, mm.' 



