82 



THE SIMPLE HOLOCARPIC BIFLAGELLATE PHYCOMYCETES 



Serbinow's study of this species relates to mate- 

 rial collected in 1913 and fixed in glycerine jelly. 

 Consequently the method of zoospore formation, 

 motility and behavior of the zoospores, relative 

 lengths and position of the flagella, as well as the 

 successive stages of sexual reproduction were not 

 observed. Whether or not it belongs in Lagenidiitm 

 is questionable. Because of the lack of or reduced 

 branching of the thallus Serbinow regarded it as 

 intermediate between this genus and Myzocytium. 

 Its method of sexual reproduction, however, seems 

 strikingly similar to that described by Dangeard for 

 Resticularia nodosa. Until more is known about L. 

 saccidoides, its relationship to the above-mentioned 

 genera will remain doubtful. Serbinow did not illus- 

 trate this species, as far as the present writer is 

 aware. Its effect on the host is quite marked. It kills 

 the desmid cells very quickly and soon destroys their 

 contents, but it is not an obligate parasite, according 

 to Serbinow. It may also attack dead and partly 

 empty cells. 



L. CYCLOTELLAE Scherffel, I.e., p. 18. PI. 2, figs. 49-59. 



Thallus small, sac-like, and continuous, attached 

 to the extramatrical persistent zoospore case by the 

 germ or infection tube; transformed completely into 

 a single sporangium at maturity, with a short, 3 jx 

 wide exit tube. Zoospores fully formed in the spo- 

 rangium ; emerging singly and swimming directly 

 away; oval, egg-shaped, 3.5 jx X 6 P> slightly con- 

 cave with a refractive mass near the posterior end ; 

 flagella attached slightly below the apex. Oospores 

 globose, 10 n, broadly oval, 8-10 p. X 10-12 p., 

 angular and somewhat irregular, hyaline, smooth, 

 thick-walled; containing a large refractive globule, 

 granular protoplasm, and a lateral spot ; germina- 

 tion unknown. 



Parasitic in Cyclotella kutzingiana in Hungary. 



The manner of zoospore formation and emergence 

 in this species are very similar to those of L. pyg- 

 maeum and L. oophilum. In shape and appearance, 

 however, the zoospores are more like those of Ectro- 

 gella bacilliariacearum, according to Scherffel. He 

 did not observe diplanetism but believed that it oc- 

 curs. Scherffel regarded this species as a connecting 

 link between Ectrogella and the Lagenidiaceae 

 (Ancylistaceae). 



L. BRACHYSTOMUM Scherffel, I.e., p. 21. PI. 2, figs. 



70-85. 



Thallus elongate, 1-7.5 ^ X 150-250 fx, usually 

 unbranched or with short side branches and pro- 

 tuberances; continuous, and transformed completely 

 into a single sporangium at maturity with one or 

 rarely two very short, tapering cone-shaped exit 

 tubes, the wall of which is greatly thickened at the 

 base to form a spreading apparatus. Exit tubes forc- 

 ing the valves of host cell apart, boring through the 

 wall. Zoospores kidney-shaped with a ventral 

 groove, 4 X 6—8 fx, formed in an extramatrical vesi- 



cle as in Pythium. Oospores formed parthenogene- 

 tically or by sexual fusion, globose, broadly-oval, 

 6— 10 fx. X 11— 24/t, hyaline, smooth, thick-walled 

 with one or two large refractive globules ; germina- 

 tion unknown. 



Parasitic in Synedra ulna, Cymbella cymbiformis 

 var. parva, Gomphonema constrictum and Nitzschia 

 linearis in Hungary (Scherffel, I.e.) and Synedra 

 sp. in North Carolina, U. S. A. (Couch, '35). 



This species differs from L. enecans, according to 

 Scherffel, by its unbranched thallus, thin wall, short, 

 cone-shaped exit tubes, and the fact that it parasit- 

 izes small diatoms. As he pointed out, however, it 

 may also occur in Cymbella cymbiformis var. parva, 

 which is also often parasitized by L. enecans. Many 

 of the structural differences which Scherffel de- 

 scribed above may possibly be due to the smaller 

 hosts in which this species lives and do not relate to 

 fundamental specific characters. Until extensive 

 cross inoculation experiments have been made, the 

 validity of L. brachysiomum must be regarded with 

 question. 



Scherffel (I.e., p. 23; pi. 2, fig. 86) further de- 

 scribed a species of Lagenidium with a long spar- 

 ingly branched, multiseptate thallus in Pinnularia 

 sp., which bears some resemblance to L. raben- 

 horstii. The exit tubes are fairly long and cylindrical 

 and extend for some distance beyond the surface of 

 the host cell. No zoospores nor their method of for- 

 mation were observed. The oospores are solitary, 

 globose and appear to have arisen by sexual fusion. 

 Scherffel was doubtful about whether this species 

 is homo- or heterothallic, but he felt certain that it 

 is not identical to L. enecans. 



L. GIGANTEUM Couch, 1935. Mycologia 27: 376. Figs. 

 1-19. 



Thallus coarse, extensive and mycelioid, 

 branched, constricted or unconstricted; extramatri- 

 cal branches somewhat fine and delicate. Sporangia 

 elongate and cylindrical, 6-40 /x X 50-300 p, with 

 a single, long 6-10 p. X 50-300 /x, exit tube; content 

 emerging through the tube to form one or several 

 globular, naked and undifferentiated masses, which 

 undergo cleavage into zoospores. Zoospores slightly 

 oval, 8-9 jii X 9—10 /x, with a ventral groove in which 

 two equal flagella are attached; freed by the rup- 

 ture or deliquescence of the vesicular membrane. 

 Monoplanetic and rather sluggish. Sexual repro- 

 duction unknown. 



Weakly parasitic on mosquito larvae, copepods 

 and Daphne in Virginia, U. S. A. (Couch, I.e.; Matt- 

 hews, '35) and mosquito in North Carolina, U. S. A. 

 (Couch, I.e.). 



Couch succeeded in growing this species on vari- 

 ous synthetic culture media and isolated what lie be- 

 lieved to be a mutant of the original strain. His is 

 the first report of the culture of a species of Lageni- 

 dium apart from its host tissues. Since sexual repro- 

 duction has so far not been observed, Couch was 

 somewhat in doubt about whether this species re- 



