78 



ings were made and it was found that a planktonic flora of some 

 extent existed. 



The taxonomic arrangement is a strictly alphabetical one, 

 by genera and by species. Eighty-four genera are included; 

 species and varieties nuinber over nine hundred. This is the 

 most extensive publication on North American Diatoms since 

 the monographic work of Charles S. Boyer, "Synopsis of North 

 American Diatomaceae," published in 1927. It is an important 

 supplement thereto, adding many new records to the North 

 American flora. In naming new species and varieties the author 

 has been moderate, an attitude which will benefit all who study 

 this difficult group. 



A feature of the report is the thoroughness with which the 

 Bibliography is compiled. In this work Mr. Hagelstein had the 

 active co-operation of an outstanding authority. Dr. John 

 Hendley Barnhart, of the New York Botanical Garden. Cita- 

 tions are taken directly from the original papers, thus errors 

 that may have arisen in the printed citations of other authors 

 are avoided. In giving the full names of the authors and the 

 years of birth and death, except in a few instances, the bibliog- 

 raphy becomes an important source of reference to diatom stu- 

 dents everywhere. Even those not primarily interested in the 

 area dealt with in the report, will find this section of the utmost 

 value. 



In recent times there has been a distinct trend toward illus- 

 tration of diatom reports by photomicrographs. When accu- 

 rately executed, a drawing leaves little to be desired. A good 

 photomicrograph is preferable to a poor drawing for it retains 

 the general character of the diatom. Depth is lost with increased 

 magnification and resolving power, but usually a plane can be 

 selected that will show the more important characters. Many 

 of the forms figured in this report are very difficult to photo- 

 graph. The figure of Pleurosigma portoricense Hagelstein, beauti- 

 fully resolved into puncta, should act as a fresh incentive to 

 ardent microscopists who seek to try their skill against the 

 diatoms most difficult to resolve. 



Mr. Hagelstein has chosen to illustrate, in addition to the 

 new species and varieties he has named, those forms of other 

 authors which have been inadequately figured or where the 

 figures appear in publications inaccessible to the general stu- 



