PARASITIC ON PELLIA EPIPITYLLA. 117 
media, and spores from a pure culture when applied to healthy 
thallus produced in it a disease like that of the original thallus. 
By means of sections the direct infection of the host by its 
upper surface was followed out and the parasitic nature of the 
fungus established. 
EXPLANATION OF THE PLATES. 
PLATE 6. 
Fig. l. Appearance of a pan of Pellia epiphylla on May 14th, 1896. The hole 
on the side is due to the removal of a sample of the thallus at the 
margin of the diseased area. From this hole the diseased area 
extends, and near that margin towards the centre of the pan are 
several small white spore-clusters in an early stage of development. 
Fig. 2. Appearance presented by the pan on June 5th, 1896, The greater 
part of the area is now involved, and the mycelium is extending over 
the surface of the part last attacked. On the diseased tissue spore- 
clusters, both white and green, are numerous, and at the parts first 
attacked rejuvenation shoots (compare figs. 3 & 5) have appeared. 
Figs. 3-5. Examples of the rejuvenation shoots produced on the thallus of 
Pellia, killed by its parasite Trichoderma. 
Figs. 6 & 7. Pieces of thallus of Pellia, showing the small diseased areas pro- 
duced by brushing spores of Trichoderma on the upper surface a 
fortnight earlier. 
Fig. 8. A piece of thallus similarly infected but kept in a dark room for the 
fortnight, 
Parte 7. 
Firs. 9. 0l | 
igs, 9 15. Germination of the spores of Trichoderma, some with two germ- 
lubes, 
Figs. 16-18, 
Hyphae of Trichoderma, some segments containing vacuolated 
protoplasm while other segments are empty. 
& 20. Formation of secondary spores, terminal and interstitial, of 
Trichoderma in cold-water extract of Pellia epiphylla thallus, in a 
coverslip culture two weeks old. 
21-25. Formation of secondary spores in a gelatine hanging-drop culture 
of Trichoderma, during its fourth week of growth and after the 
formation of conidia. 
Conidia and conidiophore removed from a spore-cluster of Trichoderma 
Figs, RAM the thallus of Pellia epiphylla. l 
“ Sitges in the formation of the termina! conidia of Trichoderma m 
Fig. 30, dome banging-drop cultures. 
Ine branching ” 
& 32. “ Cross conne > 
Figs, 19 
Figs. 
Fig, 26, 
in hanging-drop cultures. 
A preparation ; xions " in hanging-drop cultures. 
M paration, illustrating the direct infection of Pellia thallus by the 
Serm-tube of a spore of Trichoderma, and the discoloration of the cell- 
wal oo 
th 1, caused by the enzyme produced by the germinating spores and 
eir germ-tubes, ` 
Fig. 33, 
