36 PROTESTS AND DISEASE 



Writing of the genus Pytkium in general Dr. E. J. Butler 

 states : " All the species which have been investigated are 

 capable of living saprophytically. Many are capable in 

 addition to attack and destroy living tissues ; but they are 

 hemisaprophytes, for even the most destructive, P. de- 

 baryanum (Hesse), attains its maximum development -and 

 reproductivity when cultivated saprophytically." 



One species has been found to attack and destroy the 

 vinegar eelworm ; the body of which was filled with very 

 fine hyphae. In this P. anguillulae aceti sporangia, 

 conidia, and oogonia formed at the same time, not in 

 succession. 



Parasites of Pythium. The kindred of Pythium include 

 the Chytridiineae, and it happens that fungi of this latter 

 class often infect common pythiums, so that likenesses and 

 differences between host and parasite can be studied ; but 

 care not to mistake normal for parasitic features is required : 

 thus of a species of Pylhium that kills palm-trees Butler 

 wrote : " The hyphae are at first always unseptate and 

 crowded with a dense protoplasm. Fat is abundant, 

 glycogen also occurs in highiy-refractive droplets, whose 

 resemblance to Chytridiaceous fungi, parasites of the genus, 

 is remarkable." 



Pythium debaryanum. In any sowing of cress on garden 

 soil a few seedlings may be found bent down. The stalk is 

 narrowed at the bend : such a plant straightened is shown 

 in Fig. 6 ; a, where the narrow invaded part is indicated by 



