LAGENIDIACEAE 



98 



branches, confined to a single host filament or be 

 coming extramatrical and infecting several algal 

 threads. Zoosporangia no! sharply differentiated 

 (?), content-, emerging as a mass and undergoing 

 cleavage as in Pythium (':). Zoospores oval, later 

 ally biflagellate and isocont. Sexual reproduction 

 imperfectly known: two similar-sized protoplasts 

 of adjacent swellings in the same thallus fusing to 

 form spherical resting spores (oospores, zygo- 

 spores?); germination unknown. 



This genus was created by Dangeard for a fila- 

 mentous parasite of Lyngbya aestuarii found in 

 France. H<' placed Resticularia in the Lagenidiaceae 

 (Ancylistales) close to Lagenidium and Myzocy- 



tium. hut his description of its development and life 



cycle was meager and incomplete. As a result the 

 identity and relationships of this genus have been 

 the subject of much discussion and disagreement 

 among systematists in mycology who are not par- 

 ticularly familiar with the Lagenidiaceae. Saccardo 

 ('91, '12) followed Dangeard's disposition of this 

 genus, but some mycologists (Minden, 11; Fitz- 

 patrick. '80 ) regarded it as a doubtful member of 

 this group, principally because of the observations 

 of Fritsch ('03). Other mycologists (Fischer, '92; 

 Wildeman. '9(>; Schroeter. '97: Fritsch. I.e.) have 

 placed it next to Ancylistes and looked upon it as 

 related to this genus or a transition form between 

 the Lagenidiaceae and Ancylistes. The latter views 

 of course antedate tile discovery that Ancylistes be- 

 longs among the Bntomopthorales and does not re- 

 late to the Lagenidiaceae. 



Observations on a parasite found in Lyngbya in 

 the laboratories at Columbia suggest that the organ- 

 ism found by Dangeard is a valid member of this 

 family. This view is further supported by the recent 

 discovery of Couch ('41) that the zoospores of Res- 

 ticularia sp. are laterally biflagellate and isocont. 

 However, the question of whether Resticularia 

 should stand as a distinct genus or be merged with 

 Lagenidium or Mysocytium remains to be answered. 

 At present, the author is of the opinion that his 

 fungus and probably Dangeard's R. nodosa relate 



to species of Lagenidium. Further studies on the 

 method of sexual reproduction are necessary before 

 this point can be settled. The author is further of the 

 opinion that the fungus which Fritsch described as 

 R. nodosa as well as R. Roodlei ill species of Toly- 

 jjnlhri.r do not relate to Resticularia in the sense of 

 Dangeard. They are accordingly listed as doubtful 

 or excluded species. Descriptions and illustrations 

 of them are nevertheless included in plate 24 to 

 make these data available to research students. 



According to Dangeard, the zoospores are poste- 

 riorly uniflagellate, but it is not improbable that he 

 may have overlooked a second flagellum of the type 



shown ill figure I. I'Im- lar^e zoos].,, res come to rest 

 on the algal filament and form a broad germ or in- 

 fection tube which penetrates the host cells I hs;. 2 ). 



The tip of this tube elongates, increases in diameter, 



and eventually develops into the mature vegetative 



thallus i figs. 2 5) while the zoospore case remains 



on the outside. At maturity the thallus may branch 

 Several times, grow out beyond the host, and infect 

 other algal filaments. Whether or not it becomes 



septate is not obvious from Dangeard's description. 



The nuclei are rather evenly distributed along the 

 length of the thallus (fig. 7. 8). No sharply differ 

 entiated zoospora ngia were figured by Dangeard, 



which suggests that elongate segments of the thallus 



function in this capacity as in filamentous species of 



Lagenidium. At any rate the sporeplasm emerges 



through an exit tube ( lig. (i) and undergoes cleav- 

 age into zoospores. 



Very little is known about sexual reproduction, 

 and no well-defined anthcridia and oogonia have vet 



been described. According to Dangeard, the proto- 

 plasm in portions of the thallus contracts into two 

 masses in adjacent swellings (fig. 9) which fuse to 

 form oval, ellipsoidal, and spherical resting spores 

 (figs. 10. 11). Inasmuch as the protoplasts as well 

 as the swellings in which they accumulate are usu- 

 ally equal in size, Dangeard referred to the resting 

 spores as zygospores. The type of spore formation 

 shown in figure 9 is suggestive of sexual reproduc- 

 tion in Mysocytium, although intervening septa are 

 lacking. Fischer was of the opinion that if Dan- 

 geard's account of sexual reproduction is correct 

 Resticularia is to be regarded as a forerunner of the 

 Zygomycetes. 



R. NODOSA Dangeard, I.e. PI. 4, figs. 85-31 ; pi. 5, figs. 

 3,4, 



Resting spores usually numerous, oval, ellipsoidal, 

 elongate and spherical, (i-10 fi in diameter, contents 

 coarsely granular with a large refractive globule, 

 wall thick and double-layered. For additional de- 

 tails see generic diagnosis above. 



Parasitic in Lyngbya aestuarii in France, killing 

 the cells and causing the filaments to turn light yel- 

 low or colorless. 



Fritsch found a similar looking fungus in Toly- 

 pothrix in England which he took to be the same as 

 Dangeard's species. The endophytic mycelium is 

 comparatively coarse. t-o" /x, irregular, frequently 

 septate, and forms numerous brown, oval, spherical 

 and ellipsoidal, 6—9 /t. thick-walled chlamydospores 

 (figs. 12. 14), while the ectophytic mycelium is 

 much finer, 0.5—1 jjl. more branched, and bears single 

 chlamydospores on short lateral branches (tig. 13). 



Fritsch believed that the zygospores described by 



Dangeard are nothing more than chlamydospores, 



the formation of which does not involve sexual fu- 

 sion. While tin- endophytic mycelium of Fritsch's 



fungUS resembles the thallus of R. nodosa, it possi 

 bly does not relate to Dangeard's species at all since 

 Fritsch failed to observe zoosporangia or zoospores. 

 Whether the fungUS reported by Sparrow ('32) in 



filaments of Tolypothrix in Massachusetts relates to 



R. nodosa or Fritsch's organism is uncertain because 

 neither zoosporangia and zoospores nor sexual re- 

 production Were observed. 



Resticularia boodlei is apparently further re- 

 moved from Dangeard's species than the two above- 



