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 cler Achlya prolifera (Bot. Zeit., 1852). 



De Bary Einige neue Saprolegnieen (Pringsheim's Jahrb. wiss. Bot., ii.). 



De Bary Untersuch. liber die Peronosp. u. Saprolegn. (Beitr. zur Morph. u. Physiol. 

 der Pilze, iv.). 



De Bary Zu Pringsheim's Neue Beob. iiber d. Befruchtungsact cler 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 Saprolegnieae (Quart. 

 Journ. Micr. Sc., 1887). 



Hartog Recent Researches on Saprolegnieae (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. r). 



Pringsheim Beitr. zur Morph. u. Systematik 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 Saprolegniere, 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 



