10 



THE SIMPLE HOLOCARPIC BIFLAGELLATE PHYCOMYCETES 



This species is at present a doubtful member of 

 the genus, since the cystosori and resting spores are 

 unknown. It differs i'rom the other species by the 

 presence of thick greatly elongate exit tubes on the 

 zoosporangia. 



W. ASTERINA Tokunaga, 1933. Trans. Saporo Nat. 

 Hist. Soc. 13:26. PI. 2, figs. 15, 16. 



Zoosporangia 1 to 20 in number, arranged in sin- 

 gle or double rows in delimited segments of host 

 hvphae which measure 18-30X96-216^; indi- 

 vidual zoosporangia, hyaline, smooth, spherical, 

 12-19 ,u, opening by a small papilla. Zoospores hya- 

 line, spherical or ovoid, 3-4. /x; position and relative 

 lengths of flagella unknown. Resting spores loosely 

 aggregated in single or double rows, or lying free; 

 hyaline, spherical, 12-22^, with large, broadly 

 conical or pyramidal spines ; germination unknown. 



Parasitic in Achlya americana in Japan, causing 

 septation by no hypertrophy of the host hyphae. 



The validity of this species as a member of JVoro- 

 nina is highly questionable and the present writer is 

 inclined to exclude it. The resting spores and spo- 

 rangia are only loosely aggregated and often lie free 

 in the segments of the host hyphae, and they may 

 have arisen from separate individual thalli as in spe- 

 cies of Olpidiopsis. Furthermore, the resting spores 

 (fig. 14), are strikingly similar in structure and ap- 

 pearance to those of 0. fusiformis (0. minor.). Un- 

 like species of Olpidiopsis, however, TV. asterina 

 does not cause hypertrophy of the host hyphae. but 

 whether or not this character is specific remains to 

 be seen. 



PYRRHOSORUS 



similar to those of many of the simple holocarpic 

 biflagellate isocont Oomycete-like fungi, and off- 

 hand it might be regarded as a transition form be- 

 tween this group and the Plasmodiophorales. How- 

 ever, to interpret it as such does not seem fully war- 

 ranted at present, since the complete life cycle of 

 P. marinus apparently is not known. For the time 

 being, Pyrrhosorus is included in the Woroninaceae 

 as this family is herewith interpreted. 



P. MARINUS Juel, I.e., p. 14, figs. 1-29. 



Plasmodium or thallus partly or completely filling 

 host cell and extending into adjacent cells. Spore- 

 mother cells spherical, 8 yu, with numerous ref rin- 

 gent orange globules. Zoospores pyriform, 2.5 X 

 4.5 fx, with an orange pigment spot; flagella op- 

 positely directed in swimming. 



Saprophytic in dead branches of C ystoclonium 

 purpurascens in Sweden. 



The life cycle of P. marinus is as follows: In the 

 early developmental stages it consists of small glob- 

 ular thallus lying within the host cell (fig. 2). Such 

 thalli may often be associated in pairs (fig. 3) or 

 groups, and Juel accordingly considered it possible 

 that they may later coalesce and form a large Plas- 

 modium. The uninucleate thallus grows in size as its 

 nucleus enlarges (fig. 4) and apparently divides. 

 Mitoses in the plasmodium have not been observed, 

 and Juel was uncertain as to the manner of origin 

 of the multinucleate stages. A later stage is shown in 

 figure 5 of a plasmodium witli four large nuclei. The 

 developing plasmodia apparently have the ability to 

 dissolve intervening cell walls (fig. 5) and may 

 eventually occupy several cells. Although they may 

 be distinctly amoeboid in shape with numerous blunt 



Juel, 1901. Bih. Kgl. Svensk. Vet.-Akad. Hand. 

 26, afd. Ill, No. 14: 14. 



(plate 3) 



Thallus intramatrical, plasmodial, naked when 

 young but apparently immiscible with the host pro- 

 toplasm; becoming invested with a wall at maturity 

 and segmenting into spore-mother cells which ag- 

 gregate to form a sorus. Spore-mother cells divid- 

 ing three times to form octads of naked spores which 

 soon become transformed into laterally biflagellate, 

 isocont zoospores. Zoosporangia and resting spores 

 lacking (?) or unknown. 



This genus was created for an orange-colored 

 fungus which Juel found parasitizing a red alga, 

 C ystoclonium purpurascens, in Sweden. As has been 

 pointed out by the writer ('42) in his book on the 

 Plasmodiophorales, it has many characteristics in 

 common with these organisms, but differs by its lat- 

 erally biflagellate isocont zoospores, naked spore- 

 mother cells and spores; lack of zoosporangia and 

 resting spores; and by its saprophytic habit of life. 

 As is shown in figure 1 its zoospores are strikingly 



plate 3 



Pyrrhosorus marinus 



(All figures after Juel) 



Fig. 1. laterally biflagellate isocont zoospores with an 

 orange colored eye spot. 



Fig. 2. Uninucleate thallus. 



Fig. 3. Paired young thalli. 



Fig. 4. Uninucleate thallus with enlarged primary nu- 

 cleus. 



Fig. 5. Four-nucleate thallus passing through cell wall. 



Fig. 6. Multinucleate thallus. 



Fig. 7. Multinucleate amoeboid thallus. 



Fig. 8. Cleavage into spore-mother colls. 



Fig. 9. Sorus of spore-mother cells. 



Fig. 10. Isolated spore-mother ceil. 



Fig. 11. A sorus, the spore-mother colls of which have 

 divided into groups of four daughter cells. 



Fig. 12. Spindle-shaped spore-mother cells (?) in a 

 branched thallus. 



Fig. 13. Spindle-shaped spore-mother colls and acces- 

 sory sterile colls in an elongate host cell. 



Fig. 14. Sorus with spore-mother and sterile cells. 



Fig. l. r >. Nuclei of spore-mother cells dividing. 



Fig. l(i to 19. Mitosis and cytokinesis of spore-mother 

 cells. 



