.\l'll.\M)^I^^■i■:s if)7 



It is not very surprising to find another parasitic spi-cics belonging 

 to this genus, for all the previously known forms in it have shown i>ara- 

 sitic habits at times. As mentioned above we have often observed .1. 

 stellatus growing in Aclilya threads, and have found Aphauomyces laevis 

 growing on li\e desmids and diatoms. 



5. Aphanomyces phycophilus deBary. Jahrb. f. wiss, Bot. 2: 179, pi. 



20, figs. 19-24. i860. 



This interesting parasite has been reported from America by Kauffman 

 from Michigan (Ann. Rep. Mich. Acad. Sci. 17: 195. 1915) and by Weather- 

 wax ('14) from Indiana. In unpublished notes, kindly submitted to 

 us by Dr. Pieters, he says it was determined as such from an oogonium 

 found in Spirogym collected at Ann Arbor in 1913, but no culture was made, 

 nor was it found again. 



As deBary 's original treatment is long we adapt the following in great 

 part from the more condensed description by Fischer (Rabenhorst's 

 Krypt. Flora 1, part 4: 360. 1892): 



Threads stouter than in other species, 8-1 5(x thick, creeping longi- 

 tudinally through the host cells for some distance by penetrating the 

 cross walls; other threads extend outside the host and these bear the 

 reproductive organs. Sporangia threadlike, but not further described; 

 spore formation not obser\-ed. Oogonia on the ends of short threads 

 outside of the host, very rarely inside the cells; spherical, 40-50[i. thick, 

 the hyaline, unpitted wall thickly set with short, rather sharp spines. 

 Eggs spherical, single; sprouting not observed. Antheridia 1-3 on each 

 oogonium, short, club-shaped, with their tips against the oogonia, borne 

 on the ends of short branches which arise from nearby threads. 



An ol)Iigate parasite on Spirogyra and Zygnema and not to be cul- 

 tivated on insects, etc. 



Although deBary did not observe the asexual reproduction there 

 is little or no doubt that he was right in referring the plant to Aphano- 

 myces. In a short article by Weatherwax ('14, p. 109), he gives the 

 diameter of the egg as about 36(jl, its wall 3-411. thick; the spines of the 

 oogonia 5-8ix long. His plant attacked but one species of Spirogyra 

 (S. dubia), ignoring other species in the same culture. His figures 1-6 

 show oogonia and threads; he did not find sporangia. 



A problematic plant but almost certainly a species of Aphanomyces 

 is Achlyogeton solatium Cornu ('70, p. 298). It is parasitic in Oedo- 

 gonium, and may be the present species, though more apt to be dis- 

 tinct, as Fischer thinks. From Fischer we take the following con- 

 densed description ('92, p. 361): 



"Mycelium more or less branched, boring through the cross walls 

 of the host. Sporangia cut off by cross walls, not different from the 

 threads, emptying by a long emission tube which runs to the exterior; 



