346 FUNGI 



from which these arose remains, as it were, the centre of the system 

 of rhizoids, and, nourished by them, grows considerably in size. At 

 length, when it has attained full development, it becomes a prozoosporange^ 

 since from it there grows out a thick, cylindrical, thin-walled process, 

 into which all the protoplasm passes, and within which it breaks up 

 into zoospores. These, escaping, repeat the life -history. Zygosperms 

 (or oosperms) are produced by the conjugation of gametes, which play 

 unequal parts in the process. The one (supplying) individual is round 

 and larger than the other (the receptive) individual. A rhizoid from the 

 receptive individual places its apex in contact with the supplying indi- 

 vidual itself, and begins to grow in girth. The cell-wall at the place of 

 contact disappears, the protoplasm of both unites and passes into a 

 swelling which has arisen on the conjugating tube of the receiving indi- 

 vidual close behind the place of contact. This swelling then becomes 

 the zygosperm, which is provided with a thick wall, sometimes covered 

 with fine spines, appearing as early as the outset of the swelling process. 

 It happens — though rarely — that the tubes of two or three receptive in- 

 dividuals attach themselves to one supplying plant, and a corresponding 

 number of zygosperms is thus formed. After a period of rest, the zygo- 

 sperm germinates by producing a zoosporange. Generation after gene- 

 ration of zoosporanges intervene between zygosperm and zygosperm. 

 ' Which of the two should be called the male and which the female, is 

 not easy to determine. ... It is evident that we have before us an 

 intermediate case between the ordinary forms of oogamous and iso- 

 gamous conjugation.' (De Bary, loc. at, p. 163.) 



A series of incompletely -known forms may be placed beside Poly- 

 phagus (Nowak.), viz.: — Physoderma (Wallr.) [pro parte), Rhizidium 

 (A. Br.), Rhizophydium (Schenk), Obelidium (Nowak.), Chytridium 

 (A. Br.), Phlyctidium (A. Br.). Resting-cells of some of these have 

 been found, but their genesis is unknown. 



Sub-order 2 : Cladochytrie.b. — This is a small- sub-order, the 

 members of which mostly inhabit the tissues of marsh plants, and possess 

 copiously branching mycelial rhizoids, bearing terminal and interstitial 

 zoosporanges. The zoospores give rise on germination to a mycele like 

 the parent one. Resting zoosporanges occur. No process of conjuga- 

 tion is known either between filaments or zoospores. Cladochytrium 

 (Nowak.) and Physoderma {pro parte) compose the sub-order. 



Sub-order 3 : Olpidie.€. — The Olpidiese are wholly destitute of a 

 mycele, and the life-history, as described by Fischer for Olpidiopsis 

 Saprolegnise (Fisch.), and O. fusiformis (Cornu), which inhabits species 

 of Achlya, is a very simple one. The zoospores of O. Saprolegniae per- 

 forate the young mycelial hyphae of Saprolegnia, and, after a few days of 



