PAPENFUSS: CLASSIFICATION OF THE ALGAE 143 



others. Because of its brown color, the genus had for a long time been classified 

 with the Phaeophyceae (cf. Ilansgirg, 1886; De Toni, 1895). 



Long before Hydrunis had been recognized as a member of the Chrysophy- 

 ceae, a number of other genera of the class had become well known as animals. 

 The first of these (e.g., Syncrypta, Synura, Uroglena, Dinohryon) were de- 

 scribed by Ehrenberg who established the family Dinobryina for Dinohryon 

 and Epipyxis (cf. Ehrenberg, 1838). 



Stein (1878) not only added to knowledge of the genera of Ehrenberg but 

 described and illustrated several new genera belonging to this complex, includ- 

 ing the genus Chrysomonas {= ChromuUna Cienkowski, 1870). Stein was the 

 first to recognize the inten'elationship of the majority of the forms known at 

 the time of his writing. He placed the genera in the two families Dinobryina 

 (Dinohryon, Epipyxis) and Chrysomonadina (p. 152), to the latter of which 

 he referred (p. x) ten genera, eight of which are still regarded as representa- 

 tive of the Chrysophyceae. 



Biitschli (1883-1887) appears to have had little appreciation of the signifi- 

 cance of Stein's classification for he placed the genera in a number of widely 

 separated families of flagellates. Only in his assigning of Monas, Dinohryon, 

 Epipyxis, and Uroglena to a family Heteromonadina, characterized by flagella 

 of unequal length, did he attain a natural grouping. 



The greatest advance during this early period in the delimitation of the 

 group as a natural assemblage was made by Klebs (1892, pp. 394-427). He re- 

 garded the genera known in his time (including Dinohryon and Epipyxis) as 

 constituting a single family Chrysomonadina in his newly established group 

 Chromomonadina (which also included as a second family the Cryptomona- 

 dina). Klebs remarked (p. 278) that one could refer to the Chromomonadina 

 as chrysophytes, a designation which was later formally adopted by Pascher 

 (1914) as the phyletic name for the chrysomonads, heterokonts, and diatoms. 



Klebs clearly recognized the salient features w^hieh characterized the group : 

 (1) the golden-brown color of the organisms; (2) the characteristic storage 

 products leucosin (named by him, 1892, p. 395) and oil in both the pigmented 

 and the colorless members; (3) the three types of flagellation — one, two un- 

 equal flagella, or tw^o more or less equal ones; and (4) the formation of endo- 

 plasmatic cysts of a unique type such as had been observed in a number of 

 forms since they were first seen by Cienkowski (1865b). 



Although various authors (e.g., Schmitz, 1882; Rostafinski, 1882; Hansgirg, 

 1886; De Toni, 1895) before the turn of the century had regarded some of 

 the Chrysophyceae as algae (usually as Phaeophyceae), general acceptance of 

 them as a group of plants begins with the works of Engler (1898) and Senn 

 (1900). 



In agreement with the classification of Engler, Senn divided the chrysomo- 

 nads according to the number and length of the flagella into three families: 

 Chromulinaceae (with one flagellum), Hymenomonadaceae (with two equal or 

 more or less equal flagella), and Ochromonadaceae (with two unequal flagella). 



A very significant advance in the classification of the chrysomonads was 

 made by Pascher in 1910. He elevated the three groups (families) recognized 

 by Engler and Senn to the rank of order (Chromulinales, Isochrysidales, Ochro- 

 monadales) and segregated the genera into seven families. (At this time Pascher 



