138 Ulothricaceae and Chaetophoraceae 



pearing to be simply young forms have been laid aside altogether 

 until further light on them can be obtained. 



A great effort has been made to see all literature bearing upon 

 the families treated. Nearly all important works were to be 

 found in the combined libraries of Columbia University and the 

 New York Botanical Garden, or were obtained through the 

 liberality of the latter institution. Two or three articles not other- 

 wise obtainable were seen at the libraries of the Philadelphia Aca- 

 demy of Sciences and Harvard University. 



All available exsiccatae have been diligently examined, includ- 

 ing the following series : Areschoug, Algae Scandinavicae Exsic- 

 catae ; Desmazieres, Plantes Cryptogames de France ; Erbario 

 Crittogamico italiano, ser. II ; Hauck & Richter, Phykotheca 

 Universalis ; Kryptogamae Exsiccatae ; Kutzing, Algarum aquae 

 dulcis Germanicarum Decades (part only) ; Rabenhorst, Die 

 Algen Sachsens, Die Algen Europas ; Wittrock & Nordstedt, 

 Algae aquae dulcis exsiccatae ; Collins, H olden & Setchell, 

 Phycotheca Boreali-Americana ; Farlow, Anderson & Eaton, 

 Algae Exsiccatae Americae borealis ; Tilden, American Algae. 

 Naturally many of these dried specimens are very unsatisfactory, 

 but an attempt has been made to mention all American specimens 

 where their character could be determined with a fair degree of 

 certainty. 



A pilgrimage was made to Bethlehem, Pa., where, through 

 the kindness of a son of the late Mr. Wolle, we were permitted to 

 see the herbarium which formed the basis of The Fresh Water 

 Algae of the United States. Microscopical study however, was 

 made only in the case of the Ulothricaceae, which could be 

 examined without danger of marring the specimens. 



The specimens collected by Schweinitz in North Carolina pre- 

 served in the Torrey herbarium of Columbia University are for 

 the most part so old or so poorly preserved as to be unidentifiable, 

 but the collection is of less taxonomic importance than historic 

 interest, as most of Schweinitz' names were published only in J. 

 W. Bailey's lists without descriptions. 



Of specimens from miscellaneous collectors, comparatively few 

 have been seen, so that our work is based very largely upon our 

 own personal collections. 



