124 THE LOWER FUNGI— PHYCOMYCETES 



taxonomic importance of the presence or absence of the vesicle 

 here and elsewhere in the Phycomycetes. 



The genus is the largest in the order, the following species 

 being included by von Minden (1911). More recently still other 

 species have been described (Scherffel 1925). 



L. rabenhorstii Zopf (Fig. 45)- — ^in vegetative cells of Spirngijra, Mougeotia, 

 and Alesocarpuii. 



L. entophytum (Pringsheim) Zopf — in the zygospore of Spirogijra, often 

 filling it, but not found in the vegetative cells. The species L. americanum 

 Atkinson (Fig. 46) occurring in the same location is perhaps the same species. 



L. gracile Zopf — ^also in the zygospore of Spirogyra. This species has a 

 more slender, less branched thallus than the preceding. "Antheridia" are 

 absent in both. 



L. enecans Zopf — in diatoms. 



L. pygmaeum Zopf — in pollen grains. 



L. ellipticum De Wildeman — An imperfectly known and doubtful form 

 occurring in rhizoids of mosses. 



L. interniediuin De Wildeman — in Cloi^terium. 



L. closterii De Wildeman — in Closterium. 



L. syncytiorum Klebahn — -in Oedogonium. 



L. marchelianurn De Wildeman — in Oedogonium. 



4. Ancylistes Pfitzer (1872). 



The young thallus in this genus is a cylindrical tube, and may 

 be somewhat branched. At maturity it becomes septate at 

 rather regular intervals. The resultant cells may swell shghtly, 

 but deep constriction at the septa is not usual. Several thalli 

 may lie parallel in the host cell. Swarmspores are not formed 

 in the genus, and typical sporangia are lacking. The cells of the 

 thallus function either as sexual cells or vegetative cells. In 

 the latter case a slender germ tube arises from the cell, passes 

 through the wall of the host cell, and elongates into a mycelial 

 thread. This comes in contact with another host cell, bends 

 around it, penetrates it by means of a delicate infection tube, 

 and discharges its contents through this into a thin-walled 

 bladder which forms at the inner end of the tube. This bladder 

 then develops into a new thallus. The cells which develop 

 vegetatively in this manner are clearly homologous with the 

 sporangia of related genera, but they never form endogenous 

 spores. They have merely assumed the method of germination 

 usual in higher Oomycetes. 



The genus was founded on a single species, A. closterii Pfitzer 

 (Fig. 47), occurring in the desmid Closterium. In this species 



