Phylum Phaeophyta [ 77 



Order 1. Saprolegnina [Saprolengninae] Fischer in Rabenhorst Kryptog.-Fl. 

 Deutschlandl,Abt.4: 311 (1892). 

 Order Eremospermeae and suborder Mycophyceae Kiitzing Phyc. Gen. 146 



(1843), in part. 

 Order Oosporeae Cohn in Hedwigia 11: 18 (1872), in part. 

 Order Oomycetes and suborder Saprolegniineae Engler Syllab. 24 (1892). 

 Order Saprolegniineae Campbell Univ. Textb. Bot. 153 (1902). 

 Order Siphonomycetae Bessey in Univ. Nebraska Studies 7: 286 (1907). 

 Order Saprolegniales Auctt. 



Order L^p^omzfa/^?^- Kanouse in American Jour. Bot. 14: 295 (1927). 

 Aquatic Oomycetes, filamentous, saprophytic or facultatively parasitic, the zoo- 

 spores diplanetic (exhibiting two periods of swimming) or giving evidence of an 

 ancestral diplanetic condition. The old ordinal names Eremospermeae and Oosporeae 

 designated miscellaneous collections of groups in which this one was listed at or near 

 the beginning. Either one, if taken up, would be applied here, but it seems better to 

 treat them as nomina confusa. 



1. Filaments not constricted Family 1. Saprolegniea. 



1. Filaments constricted at intervals. 



2. Filaments not differentiated into basal 



and reproductive parts Family 2. Leptomitea. 



2. Filaments differentiated into basal and 



reproductive parts Family 3. Rhipidiacea. 



Family 1. Saprolegniea [Saprolegnieae] Kiitzing Phyc. Gen. 157 (1843). Family 

 Saprolegniaceae Cohn in Hedwigia 11 : 18 (1872). Aquatic Oomycetes consisting of 

 branching filaments of essentially uniform diameter without crosswalls other than 

 those which set apart differentiated reproductive structures. 



These well-known organisms are called water molds. According to Coker (1923) 

 there are about eighty definitely recognizable species. They may be parasitic on 

 fishes or saprophytic on organic remains in water or soil. In almost any body of soil 

 or of fresh water they may be found by "baiting," in former practice with dead flies, 

 currently with hemp seeds. 



Mitosis has rarely "been observed in the vegetative filaments, the nuclei being very 

 minute. Eggs are produced in large globular multinucleate oogonia borne at the ends 

 of filaments. The nuclei in the developing oogonia become enlarged and undergo a 

 single flare of concurrent mitoses (Davis, 1903; Couch, 1932). The sharp-pointed 

 spindles, ending in centrosomes, are formed within the nuclear membrane. The 

 membrane disappears toward the end of the mitotic process, and a nucleolus, which 

 has persisted to this stage, undergoes solution in the cytoplasm. The chromosome 

 numbers (Ziegler, 1953) are 3, 4, 5, 6, or 7. 



Within each oogonium there appear one or a few minute bodies called coenocentra. 

 One nucleus becomes associated with each coenocentrum; all others break down and 

 disappear. Each surviving nucleus with the cytoplasm associated with it becomes 

 organized as an egg. When several eggs are produced, they share all of the cytoplasm 

 of the oogonium; when only one egg is produced, some of the cytoplasm is left out- 

 side of it. 



Sperms are produced in small multinucleate antheridia borne at the tips of fila- 

 ments in contact with oogonia. Typically, each individual bears both oogonia and 

 antheridia. Some species are capable of self-fertilization; others exist as two kinds 

 of individuals, each capable of fertilizing the other; some occur as distinct male and 



