14 



THE SIMPLE HOLOCARPIC BIFLAGELLATE PHYCOMYCETES 



similar to that of Rozella. The portions of the thal- 

 lus or "plasrnodium" in the hypertrophied hyphal 

 segments or swollen side branches appear to con- 

 tract and become invested with a wall (fig. 19), so 

 that they lie loose and free in the host cell. The in- 

 cipient spores usually lie in a clear space which in 

 turn is surrounded by a layer of host cytoplasm (fig. 

 20) from which strands radiate to the periphery. 

 The clear area is apparently the region in which 

 the host cytoplasm is transformed into spore wall 

 material, because as the cytoplasm decreases in 

 amount definite spines are deposited on the outer 

 wall of the spore (figs. 20, 21). The spines and 

 echinulations seem thus to be nothing more than 

 modified host protoplasm as Butler ('07) and Mc- 

 Larty ('41) have shown in Olpidiopsis Pythii and 

 0. Achlyae. Germination of the resting spores has 

 not been observed, but they probably give rise di- 

 rectly to zoospores as in Rozella. 



As is shown in plate 1, Rozellopsis produces a 

 marked reaction in the host hyphae which involves 

 both cell enlargement and cell division. Hyper- 

 trophy is local and confined largely to the region of 

 infection. According to Miss Waterhouse's figures 

 (figs. 5—7) it may even begin during infection. 

 Eventually the infected portions of the hyphae may 

 become ten to fifteen times their normal diameter 

 (figs. 1—3) and are usually delimited from the re- 

 mainder of the mycelium by cross walls (figs. 9-12, 

 16, 17, 22). Such cross septa may become unusually 

 thick (figs. 11, 12) and in extreme cases project up 

 or down into the hypertrophied portions as dome- 

 .shaped plugs. In the cases of infection by septi- 

 genous species the fragments of the "plasrnodium" 

 are successively delimited by walls, so that an in- 

 fected hyphal tip may have a large number of cross 

 septa (figs. 17, 22). The reaction of the host nuclei 

 and cytoplasm to the presence of the parasite is not 

 known, since most studies to date have been made 

 on living material. However, as noted previously, 

 Fischer believed that the two protoplasts mix and 

 become indistinguishable, but this seems unlikely. 



The taxonomic position and relationship of Rosel- 

 lopsis to the simple holocarpic biflagellate fungi are 

 very uncertain at present, and solution of these ques- 

 tions must await further study. In view of the re- 

 ports that its thallus is a plasrnodium which under- 

 goes schizogony in the septigenous species, Rozel- 

 lopsis is herewith included provisionally in the fam- 

 ily Woroninaceae in the restricted sense noted above. 

 This disposition is obviously temporary and may be 

 completely invalidated by future studies. The pres- 

 ence of a plasmodium which may undergo fragmen- 

 tation still remains to be demonstrated in Rozellop- 

 sis, in the writer's opinion. If schizogony does occur 

 in the septigenous members it may become necessary 

 to segregate them in a separate genus. The presence 

 of anteriorly biflagellate heterocont zoospores in R. 

 simulans suggests direct affinity with the Plasmodio- 

 phorales, but this relationship likewise remains to 

 be proven. 



Aseptigenous Monosporangiate Species 



R. INFLATA (Butler) Karling, 1943. Amer. Jour. Bot. 

 29 :34. 

 Pleolpidimm inflatum Butler, 1907. Mem. Dept. Agric. 

 India. Bot. ser. 1: 126, 127, pi. 7, figs. 17-31. 



Sporangia terminal, spherical, up to 85 /jl in di- 

 ameter, oval, or pyriform with one to several exit 

 papillae. Zoospores reniform, kidney-shaped with 

 the shorter flagellum attached at the anterior end 

 and the longer one at the side ; swimming smoothly 

 in long curves. Resting spores unknown. 



Parasitic in Phytium intermedium, Antibes, 

 France, causing marked hypertrophy of the host 

 sporangia. 



R. WATERHOUSEII Karling, I.e., p. 34. 



Sporangia terminal, spherical, up to 74 /x in di- 

 ameter, clavate, oval, or obpyriform with 1-3 apical 

 or lateral exit papillae. Zoospores pyriform, 5-8 /x 



plate 4 



Bozellopsis inflata 



(Figs. 1-4 after Butler, '07; figs. 5-14 after Miss Water- 

 house, '40; figs. 15-21 after Fischer, '82; figs. 22, 23 

 after Tokunaga, '33.) 



Fig. 1. Sporangia in the hyphal tips of Pythium inter- 

 medium. 



Fig. 2. Zoospores within a sporangium. 

 Fig. 3. Empty sporangium. 



Fig. 4. Heterocont zoosi>ores with one or two refractive 

 globules at the ends. 



R. waterhouseii 



Figs. 5-7. Infection of hyphal tip of Phytophthora cryp- 

 togea. 



Fig. 8. Early stage of hypertrophy. 



Fig. 9. Later stage. Sporangium of parasite delimited 

 by cross septa, multivacuolate with one exit papilla. 



Fig. 10. Still later stage in which the vacuoles have 

 fused to form a large central one. 



Fig. 11. Sporangium with zoospore initials. 



Fig. 12. Zoospores swarming in the sporangium and 

 emerging through the exit orifice. 



Figs. 13, 14. Heterocont motile, and encysted zoospores. 



R. septigena 



Fig. 15. Heterocont zoospores with one refractive glob- 

 ule. Shorter flagellum at anterior end. 



Fig. 16. Multiple infection of Baprolegnia hyphal tip. 



Fig. 17. Hypertrophied and septate host hypha with 

 several "Reihensporangien" in various stages of develop- 

 ment. 



Figs. 18-21. Stages in development of the resting spores. 



7?. simulans 



Fig. 22. Infected hypha of Achlya flagellata with spo- 

 rangia in various stages of maturity. 



Fig. 23. Anteriorly biflagellate heterocont zoospores 

 with a refractive globule. 



