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; Desmaziéres, Plantes Cryptogames de France; Erbario 
Crittogamico italiano, ser. II; Hauck & Richter, Phykotheca 
Universalis ; Kryptogamae Exsiccatae ; Kützing, Algarum aquae 
dulcis Germanicarum Decades (part only); Rabenhorst, Die 
Algen Sachsens, Die Algen Europas; Wittrock & Nordstedt, 
Algae aquae dulcis exsiccatae; Collins, Holden & 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. 
