OOMYCETES 335 



The modes of zoospore-formation in Phytophthora and Cystopus, 

 Pythium Achlya, and Aphanomyces, Dictyuchus, and lastly Saprolegnia, 

 express in an interesting way the relationships of these genera. 



Literature. 



De Bary — Beitr. zur Kenntniss der Achlya prolifera (Bot. Zeit., 1852). 



De Bary — Einige neue Saprolegnieen (Pringsheim's Jahrb. wi.ss. Bot., ii.). 



De Bary — Untersuch. uberdie Peronosp. u. Saprolegn. (Beitr. zur Morph. u. Physiol, 

 der Pilze, iv. ). 



De Bary— Zil Pringsheim's Neue Beob. liber d. Befruchtungsact der Gattungen Achlya 

 und Saprolegnia (Bot. Zeit., 1883). 



Cornu — Monograph, der Saprolegn. (Ann. Sc. Nat., 1872). 



Hildebrandt — Mycolog. Beitrage, i. (Pringsheim's Jahrb. wiss. Bot., vi. ). 



Hartog — On the Formation and Liberation of Zoospores in the SajDroIegnieEe (Quart. 

 Journ. Micr. Sc, 1887). 



Hartog — Recent Researches on Saprolegniese (Annals of Botany, 1888). 

 -Huxley and Murray — Salmon Disease (Reports of Inspector of Fisheries, 1882, 1883, 

 .1884, 1885. See also Quart. Journ. Micr. Sc, 1882, and Journ. Bot., 1885). 



Leitgeb — Neue Saprolegnieen {ibid., vii. ), 



Lindstedt — Synopsis der Saprolegn., Berl., 1872. 



Pringsheim— Entwickelungsgeschichte der Achlya prolifera (N. Acta Acad. Leop. - 

 Carol., xxiii. , p. i). 



Pringsheim — Beitr. zur Morph. u. Systeraatik d. Algen, ii. Die Saprolegn. (Jahrb. 

 wiss. Bot. , i. , ii. , and ix. ). 



Pringsheim — Neue Beobacht. iiber d. Befruchtungsact von Achlya u. Saprolegnia 

 (Sitzber. Berl. Acad., 8 Juni, 1882). Nachtragliche Bemerk. zu dem Be- 

 fruchtungsact von Achlya (Pringsheim's Jahrb. wiss. Bot., xiv.). 



Reinsch — Beobacht. iiber einige neue Saprolegn. {ibid., xi.). 



Thuret — Rech. sur les zoospores des Algues, 1851. 



Ward — On Saprolegnieas, and also on Pythium (Quart. Journ. Micr. Sc. , 1883). 

 Contain histological details. 



Class XIX. — Zygomycetes. 



Order i. — Mucorini. 



The Mucorini are for the most part terrestrial saprophytes, the re- 

 mainder being parasites on other Mucorini. The thallus consists of a 

 copiously branching hypha undivided up to the time of the production 

 of spores or sporanges, when transverse walls first appear. Sexual repro- 

 duction is effected by the formation of a zygosperm, while spores and pro- 

 pagating cells (like some of the resting-cells produced by the mycele of 

 Saprolegnia) are also borne, the former regularly and in characteristic 

 forms, the latter only in special cases and under certain conditions. The 

 production of a zygosperm is effected by the conjugation of two specially 

 differentiated cells, gametes, not to be distinguished from each other by 

 any mark or power of movement. The two cells thus contributing to 



