Pred8c.funp;i:3 



stuck. There is no question, I think, of any sticky substance bein;^ 

 secreted. It is just that the eelworm has not enough sense to v/ith- 

 draw. It just tries to force its way through the ring with the ob- 

 vious result; it gets well and truly wedged. 



The supporting stalk of the ring is rather slender, and it quite often 

 happens that a captured eelworm will tear the ring away from its moor- 

 ings and thus get away. I have seen eelwroms in cultures with as many 

 as half a dozen rings encircling them like dog collars, showing that 

 they had been caught half a dozen times and escaped. Actually, the 

 escape is only temporary, because, even from a detached ring, hyphae 

 will ultimately grow out, penetrating into the eelworm and killing it. 

 l^Ihere it has happened that the ring has been detached from the mycelium 

 and the eelworm has been killed, a new mycelium grows out from the ring. 

 Thus, these rings can actually serve as a means for reproduction, as 

 well as for capturing prey. 



Now we come to the most dramatic type of eelvrorm trap, the constricting 

 ring. This is formed in exactly the same way as the non- const rioting 

 ring, but it is rather more stout in construction and has a shorter, 

 sturdier stalk. In this type of trap, the fungus does not depend upon 

 the efforts of the eelworm to get it wedged into the ring. The three 

 cells of the ring are sensitive to touch and to friction. The friction 

 of an eelworm 's body that has put its head into a ring is sufficient to 

 trigger off the reaction. The three cells suddenly expand inwards, in- 

 creasing to about as much as three times their previous volume. The 

 opening in the ring becomes com.pletely occluded. The eelworm caught 

 in the contricting loop quite rapidly dies. Hyphae develop from the 

 cells of the ring and grow into the body of the eelworm, consuming its 

 contents and passing them back to the main part of the fungus. 



The closure time for the ring is very rapid, being about l/lO of a 

 second from beginning to complete closure. Immediately after closure 

 there is the formation of nvimerous small vacuoles which run together 

 and form a globule of glistening, highly refractive material. We do 

 not know what this material is or what is the mechanism for ring closure. 

 I do not think it is osmotic. 



A curious thing that I have observed in agar cultures is that these 

 rings are often formed just beneath the surface of the agar and are 

 oriented in a vertical plane. The eelworms move in this area of the 

 surface so that the rings are in a good oosition to capture the eel- 

 worms. IVhat mechanism insures that the rings shall be perpendicular, 

 I just do not know. It is certainly not gravity, because the agar 

 plates can be stored in any position, and the rings will still orient 

 themselves peipendicularly to the surface. 



We have discussed the principle types of eelworm trapping fungi. They 

 belong to four genera: Arthrobotrys , Tricothecium , Dactylella , and 

 Dactylaria; four very closely related genera which differ only in the 

 shape, septation, and mode of formation in their conidia. 



