PROGRESS AND ACHIEVEMENTS IN PHYCOLOGY 561 



kontae. The currently accepted name Xanthophyceae was proposed by AUorge 

 (1930). 



Following the pioneering studies by Borzi, Bohlin, and Luther, many in- 

 vestigators of the present century, but especially Pascher, have made impor- 

 tant contributions to our knowledge of the Xanthophyceae. The present sys- 

 tem of classification of the group is essentially that of Pascher (1912, 1925, 

 1937-1939). In accordance with the morphology of the thallus, he established 

 orders which parallel certain chlorophycean orders. He erected the order 

 Heterochloridales to receive the flagellated genera, the Rhizochloridales for 

 the amoeboid forms, the Heterocapsales for the palmelloid members, the 

 Heterococcales for the coccoid types, the Heterotrichales for the filamentous 

 representatives, and the Heterosiphonales (now known as Vaucheriales) for 

 the siphonous taxa. 



Significant observations favoring Pascher's belief in a relationship between 

 the Xanthophyceae and Chrysophyceae were made by Vlk (1931, 1938). He 

 showed that the biflagellate cells of the Xanthophyceae conform to those of 

 the Chrysophyceae in that the long flagellum is of the tinsel type, being beset 

 with two rows of delicate cilia, whereas the short flagellum lacks cilia. 



A further character in support of such an alliance was brought into the 

 foreground by Pascher in 1932. He pointed out that the bivalved cysts which 

 he had discovered in certain Xanthophyceae were comparable to the bottle- 

 like cysts (replete with bung) characteristic of the Chrysophyceae. 



Blackman in 1900 brought attention to the fact that Vaucheria appeared 

 to be the only "green" alga outside the Heterokontae which had chlorophyll 

 possessing the same characters as in members of the Heterokontae. In 1901 

 Bohlin formally removed Vaucheria to the Heterokontae. He pointed out, 

 among other things, that it had long ago been shown that the sperms of 

 Vaucheria possess two flagella of unequal length. In general, botanists have 

 preferred to retain Vaucheria in the Chlorophyceae, but recent work by Sey- 

 bold, Egle, and Hiilsbruch (1941) and Strain (1948) on the pigments and by 

 Koch (1951) on the structure of the flagella of the sperm has shown that 

 Vaucheria can no longer be classified with the green algae. This is incon- 

 venient, for it has removed from the green algae the classical example of a 

 siphonous and oogamous "green" alga and one that is readily obtained for 

 classroom study. 



Chrysophyceae. With the exception of the genera Hydrurus and Phaeo- 

 thamnion, which had been placed in the Phaeophyceae, the Chrysophyceae 

 that became known during the last century were usually regarded as animals 

 and were ignored by botanists. As was so often true during that period, 

 Klebs was the first botanist to make a thorough study of some of these 

 organisms. In 1892 he clearly recognized the salient features that characterize 

 the group: (1) the golden-brown color of the organisms; (2) the character- 



