Phylum Phaeophyta [ 65 



the type group of the class. As established by Luther, the class consisted of the new 

 genus Chlorosaccus together with a few genera of flagellates ( Vacuolaria was included 

 in error) and a few transferred from the group of typical green algae. From time to 

 time, other green algae have been transferred, and it has become evident that the 

 group is a fairly extensive one. Green organisms can be recognized as belonging here 

 by a negative reaction to the iodine test for starch, and by the fact that they give a 

 b'uish color when heated with hydrochloric acid, instead of a yellow one, as typical 

 green algae do: the difference depends upon differences in the complement of 

 photosynthetic pigments. Bohlin (1901) placed Vaucheria here; most authors have 

 not followed him, but Smith (1950) has done so. This genus brings with itself the 

 oldest name for the group as an order. 



Mitosis in Vaucheria was described by Hanatschek (1932) and Gross (1937). The 

 spindle is intranuclear; Hanatschek saw centrosomes at the poles. The conjugation of 

 equal free-swimming gametes was observed in Tribonema and several other genera by 

 ScherfFel (1901), and in Botrydium by Rosenberg (1930). Vaucheria was one of the 

 organisms by study of which the nature of fertilization was discovered (Pringsheim, 

 1855). Hanatschek and Gross found that the first two divisions of the nucleus of 

 the zygote are meiotic: the soma is haploid. 



This order is believed to represent the direct ancestry of the two following classes, 

 Bacillariacea and Oomycetes. 



Pascher (1912, 1925) arranged the green Heterokonta in subordinate groups 

 parallel to those of the typical green algae; and, as the main groups of green algae 

 are treated as orders, he treated these groups also as orders (in 1931 as classes). 

 They are scarcely entitled to such rank: too many of the classes or orders are of 

 single families, and too many of the families are of one or two genera. Here, then, 

 Pascher's classes and orders are suppressed and several of his families are reduced. 

 1. Not truly filamentous nor producing rhizoids. 

 2. The cells walled. 



3. Cells regularly dividing into two, 

 forming gelatinous colonies; occa- 

 sionally producing small numbers 

 of zoospores. 



4. The colonies globular or Irreg- 

 ular, becoming macroscopic Family 1. Chlorosagcacea. 



4. The colonies dendroid, micro- 

 scopic Family 2. Mischococgacea. 



3. Cells normally undergoing division 

 into several. 



4. Producing zoospores Family 3. Chlorotheciacea. 



4. Producing no motile cells Family 4. Botryococcagea. 



2. The cells loricate Family 5. Stipitogogcacea. 



2. The cells amoeboid Family 6. Chloramoebacea. 



1. Filaments of uninucleate cells Family 7. Tribonematagea. 



1. Cells becoming highly multinucleate, form- 

 ing filaments or at least producing rhizoids Family 8. Phyllosiphonacea. 



Family 1. Chlorosaccacea [Chlorosaccaceae] Smith Freshw. Algae 145 (1933). 

 Family Heterocapsaceae Pascher in Hedwigia 53: 13 (1912); there is no correspond- 

 ing generic name. Gelatinous aggregates of cells which may divide, causing the 



