126 THE LOWER FUNGI— PHYCOMYCETES 



germ tubes marks it as the most highly developed member 

 of the order. 



Knowledge of the nuclear history in the genus rests wholly on 

 the work of Dangeard (1906) on A. closterii Pfitzer. He pictures 

 the young thallus as plurinucleate, the nuclei being regularly 

 spaced in a single row in the thread. In the segmentation of 

 the thallus each cell receives several nuclei. In the beginning, 

 each vegetative cell contains four or five nuclei, but the number 

 is doubled by a single simultaneous mitosis. The eight or ten 

 resultant nuclei pass over with the cytoplasm through the germ 

 tube and infection thread into the new host cell. The male 

 gametangium at first usually contains two nuclei while the 

 female possesses six or eight, A single simultaneous division 

 later doubles the number in each. The nuclei and cytoplasm of 

 the male cell enter the female, but nuclear fusion apparently 

 fails to occur. The resting spore matures in the plurinucleate 

 condition, containing both male and female nuclei. It is possible 

 that a fusion occurs at the time of germination, though it has 

 not been seen. Germination is by tube (Dangeard, 1886). 



Doubtful or Excluded Genera 



1. Resticularia Dangeard (Le Botaniste, 2: 96, pi. 4, 1891). 

 This genus was based on a single species, R. nodosa Dang. 



(Fig. 48), found parasitic in Lynghya. It was accepted by 

 Fischer (1892: 84) and Schroter (1893: 92), both authors placing 

 it next to Ancylistes. Later this species was discovered by 

 Fritsch (1903 : 649) in England growing in Tolypothrix, and was 

 redescribed by him. He states that it occasionally forms 

 sporangia containing uniciliate swarmspores. He also described 

 as new another species, R. boodlei Fritsch, found in the same 

 host. The genus is listed by von Minden (1911 : 444) as a doubt- 

 ful member of the Ancylistales. In the present state of our knowl- 

 edge a satisfactory disposition of it cannot be made. 



2. Rhizomyxa Borzi. 



Discussed above under Sorosphaera of the Plasmodiophoraceae. 



3. Lagenidiopsis De Wildeman (Ann. Soc. Beige Micros., 20: 109, 



1896). 

 A single imperfectly understood species, L. reducta De Wild., 

 found in oogonia of Characeae. 



