S6o PAPENFUSS 



morphology and interrelationships of this large and diversified class. Despite 

 certain shortcomings (cf. Papenfuss, 1951; Drew, 1954a) his system allows 

 of a much more natural arrangement than had previously been possible. 



In Kylin's (1932) system the orders are separated on whether a generative 

 auxiliary cell is absent or present, its time of formation — before or after fer- 

 tilization of the carpogonium — and its manner and place of formation. 

 Whether or not the importance of this cell has been overemphasized in the 

 creation of this system can only be determined from further work on the 

 morphology of the many genera that await investigation. Since the generative 

 auxiliary cell is the starting point of a generation, the carposporophyte, there 

 at present appears to be ample justification for believing that the absence or 

 presence of this cell and the characters associated with its formation are 

 matters of the utmost importance in the establishment of major taxonomic 

 categories. 



CHRYSOPHYCOPHYTA 



This phylum was erected by Pascher in 1914 (cf. also Pascher, 1921). It 

 includes the three classes Xanthophyceae (known until 1930 as Hetero- 

 kontae), Chrysophyceae, and Bacillariophyceae (commonly known as dia- 

 toms). Although the pigmented members of these three groups usually have 

 yellow-green or golden-brown chromatophores and it has consequently been 

 assumed that they possess similar pigment complexes, it is now known from 

 the work of Strain (1951, p. 253) and others that there are significant differ- 

 ences. On the basis of pigment composition as well as structure of the cell 

 and life history, the diatoms, at best, appear to be only distantly related 

 to either the Xanthophyceae or the Chrysophyceae. 



Xanthophyceae. The few Xanthophyceae that had become known previ- 

 ous to 1899 were regarded as green algae by botanists, and they were placed 

 in widely separated families. Borzi in 1895 brought them together in an order 

 Confervales, mainly on the basis of three characters: (1) they possessed dis- 

 coid yellowish-green plastids; (2) they did not store starch; and (3) their 

 zoospores had only one flagellum (as he believed). 



In the course of the next few years Bohlin (1897a, 1897b) and Luther 

 (1899) produced evidence which showed that the characters whereby the 

 Confervales differed from the green algae were of such magnitude that they 

 could no longer be classified with them. It was established that they differ 

 from green algae not only in pigment composition and storage products, but 

 that the two overlapping pieces that form the lateral wall of the cells have 

 a layered structure and that the wall is not composed of cellulose but of a 

 pectic acid derivative. It was also shown that the motile cells are actually 

 biflagellate, with the one flagellum much shorter than the other. Luther (1899) 

 consequently erected for these algae a separate class, which he named Hetero- 



