Phylum Phaeophyta [ 69 



Order 5. Hyphochytrialea [Hyphochytriales] Bessey Morph. and Tax. Fungi 69 

 (1950). 

 Order Anisochytridiales Karling in American Jour. Bot. 30: 641 (1943), not 

 based on a generic name. 



Non-pigmented organisms with walled cells, parasitic or saprophytic, the proto- 

 plasm with numerous granules not of a shining appearance, producing zoospores 

 with single anterior pantoneme flagella. 



The naked zoospores come to rest upon appropriate hosts or substrata. Ordinarily, 

 in parasitic species, the protoplast of the zoospore makes its way to the interior of a 

 cell of the host. It swells and develops a thin wall. The resulting structure may be 

 called a center. In most members of the group, the center gives rise to a system of 

 slender rhizoids; in some species, these give rise to further centers like the original 

 one. Karling studied the cytology particularly in Anisolpidium. There are repeated 

 simultaneous mitoses in the growing centers. Resting nuclei contain conspicuous 

 karyosomes. Dividing ones show about five chromosomes in an intranuclear spindle 

 which ends sharply in centrosomes. Eventually, in the usual course of events, each 

 center produces an exit tube to the exterior. Its contents are released by delique- 

 scence of the tip of the exit tube. Either before this or afterward, the mass of proto- 

 plasm undergoes cleavage into uninucleate protoplasts which generate flagella. Some- 

 times, instead of discharging their contents, the centers are converted into resting 

 spores by the secretion of thick walls (this has been observed in only a few of the 

 species). The resting spores germinate by producing exit tubes and discharging 

 zoospores as ordinary centers do. 



The body type which has just been described may be called the chytrid body 

 type; organisms of this body type were formerly assembled as a taxonomic group 

 typified by the genus Chytridium. Couch, however, showed that these organisms 

 form three groups distinguished by fundamental differences in type of flagellation. 

 The present group is here given a place implying relationship to order Silicoflagellata. 



Karling (1943) accounted for fourteen species. He provided three families; only 

 one is here maintained. 



Family Hyphochytriacea [Hyphochytriaceae] Fischer in Rabenhorst Kryptog.-Fl. 

 Deutschland 1, Abt. 4:131 (1892). Families Anisolpidiaceae and Rhizidiomycetaceae 

 Kailing in American Jour. Bot. 30: 641, 643 (1943). Characters of the order. 

 Without rhizoids: Anisolpidium on brown algae; Roesia on Lemna; Cystochytrium 

 on roots of Veronica. With rhizoids from a single center: Rhizidiomyces and Latr os- 

 tium on green algae, aquatic fungi, and the empty exoskeletons of insects. With 

 multiple centers: Hyphochytrium and Catenariopsis, on fungi and other hosts. 



Class 2. BACILLARIACEA Engler and PrantI 



Homalogonata Lyngbye Tent. Hydrog. Danicae 177 (1819). 

 Order Diatomeae C. Agardh Syst. Alg. xii (1824). 



Division (of order ^/gae) Diatomaceae Harvey in Mackay Fl. Hibem. 166 (1836). 

 Family Bacillaria Ehrenberg Infusionsthierchen 136 (1838). 

 Series (of class Algae) Diatomaceae Harvey Man. British Alg. 15 (1841). 

 Abtheilung (of cldiS,?, Isocarpeae) Diatomaceae Kiitzing Phyc. Germ. 54 (1845). 

 Stamm Diatomea Haeckel Gen. Morph. 2: xxv (1866). 



Division (of class Algae) Diatomaceae Rabenhorst Kryptog.-Fl. Sachsen 1: 1 

 (1863). 



