Chapter XI 

 CARNIVOROUS FUNGI 



Occurrence. — Habit. — Glands. — Secretion. — Digestion. 



Among the multifarious activities of fungi, that of zoophagy has 

 been well known for a very long time. Of this one of the best known 

 examples is the behavior of Cordyceps, which invades the bodies of 

 caterpillars of various species and sizes. After displacing the substance 

 of the body of the larva attacked, preserving its form, however, in the 

 sclerotium thus formed, the fungus then sends up a linear stalk bearing 

 the fruiting bodies, the sclerotium being buried in the soil (since 

 it was there that the larva was destroyed), and the fruiting stalk 

 rising above in free air. The study of this kind of pathology in rela- 

 tion to lower forms (algae, small water animals) was being pursued 

 by the botanist, W. Zopf, in Austria, when there came to his atten- 

 tion just previous to 1888 a fungus which attacked eelworms {Anguil- 

 lulidae) . 



In the various cultures which he was observing, there were numer- 

 ous living eelworms and many dead ones tangled with and variously 

 penetrated by the hyphae of the fungus. The question then arose 

 in his mind as to whether the fungus is purely saprophytic, pene- 

 trating only already dead worms, or does the fungus attack and kill 

 the Kving animal? In answering this question experimentally, Zopf 

 made the first discovery of a fungus which traps a living animal. 



The fungus was Arthrohotrys oligospora, first described by Fres- 

 ENros (1850-63). It is found in all kinds of more or less decayed 

 matter — mats of old algae for example — and makes a thin veil of 

 mycelium of septate hyphae over the surface. From it there 

 extend slender septate conidiophores bearing pear-shaped two-celled 

 spores. The peculiar feature is the occurrence on the hyphae of many 

 slings or loops of various sizes, formed by the sharp curving of a 

 growing branch which turns upon itself and fuses by its end with its 

 base. From one loop a second and from this a third may arise, and 

 thus is formed a tangle of loops lying in all positions, as Woronin 

 had already observed. It was Zopf, however, who first saw that 

 living eel-worms were actually caught by these loops, either by the 

 tail or by the head. The fact that when once the worm has by chance 

 inserted one end or the other into a loop, it cannot free itself again, 

 was definitely observed. The eelworm he used was Telenckus scandens, 

 which infests wheat. One observed, on being caught, struggled vio- 

 lently for a half-hour, then became quieter and finally died in 2.5 

 hours. Why the eelworm cannot free itself when once trapped he 

 attempted to explain by analogy, using as a model a rubber loop 

 just big enough to allow a finger to enter. When one attempts to 

 withdraw the finger, the rubber band clamps on the surface and holds 

 the finger. The clamping effect is due to springiness of the loops, he 



