Predac .fungi :4 



In Arthrobotrys , as in Tricotheciun , there is a two-cell spore. In 

 Arthrobotr.ys the spores are ronned in a whorl at the apex of the 

 erect conidiophore. The arrangement is definitely capitate, that is, 

 a definite group at tne tip. There may be successive whorls do\m the 

 conidiosphre. Tricothecium has similar spores, but in Tricotheciun , 

 unlike Arthrobotrys , which has a terminal spore and then more spores 

 formed do-vm the conidiophore, spores are evidenced more as though on 

 an ear of corn than as a series of whorls. 



i»actylella and Dactylaria both have spores with more than two cells; 

 and in both genera the spores may be cigar-shaped, or they may be top- 

 shaped, in which case they always have one cell very much bigger than 

 the others. To distinguish between Dactylella and Sactylaria is quite 

 impossible. I have been trying to do it for twenty years, and I have 

 Tiot succeeded yet. Theoretically, and mind you, I say theoretically, 

 in Dactylella there is a single spore at the tip of the conidiophore, 

 i^hereas in Dactylaria there is a group. Unfortunately, every Dact y- 

 i.ella I have ever examined forms two or three conidia on its conidio- 

 ohores; and, on the other hand, in many Dactylaria the whorl arrange- 

 'Tent is very lax. It is, therefore, impossible to really distinguish 

 it from a Dactylella having more than one spore. Personally, I think 

 they should have been the same genera, and no doubt they will be one 

 day. 



Now just one or two points about the physiology of these fungi which 

 might be of importance if they are to be used for eelworm control. 

 First of all, they can all be grown easily in culture, like any other 

 saprophytic fungus. Most of them, when grown in pure culture, do not 

 form the characteristic eelworm traps; but they do so if they are 

 brought into contact with eelworms, or if they are given a little 

 sterile water in which eelworms have lived. They are perfectly able 

 to exist as saprophytes, tfe do not know yet in what way they mainly 

 exist in nature, whether they occur in the soil as saprophytes and 

 only occasionally capture an eelworm, or whether they depend mainly 

 upon eelworms as a diet. My own personal opinion is, judging from 

 indirect observation in cultures, that it is a question of available 

 food. 



There seems to be quite a delicate balance between the predacious and 

 the saprophytic phases of the activity of these fungi. I do not know 

 yet exactly what it is that effects that balance and decides which type 

 of activity they are going to show, but one of the things that can 

 effect it is the presence of eelworms. If one takes a culture of the 

 predacious fungi and feeds it eelworms, usually the fungus will simply 

 remain in the saprophytic state. On the other hand, if one proceeds 

 in the converse way, the result is different. If one has a very good 

 culture of saprophytic eelworms, say on rabbit dung agar, and if it is 

 really so filled with eelworms that no ordinary mold could grow on it, 

 and if one puts on such a plate a very small piece of inoculum of a 

 predacious fungus, then one finds that the fungr.s will thrive on the 

 eelworms. It seems to me quite clear that there must be somothnng in 



