486 BOTANICAL GAZETTE [DECEMBER 
he considers the lichen to consist of the fungus and the alga on which it grows, 
instead of accepting the logical view, namely, that the fungus alone constitutes _ 
the lichen. 
Phacopsis vulpina Tul. and Karschia destructans Tobler, of the Pezizineae, 
are considered with respect to their biological relation to the lichens on which 
they grow and to the algal hosts of these lichens. Phacopsis vulpina is found 
on the thallus of Evernia vulpina (L.) Ach. in the Alps. By sectioning the 
fungus and the lichen host together in paraffin and subsequent treatment with 
iodine solution, the author was able to trace the course of the Phacopsis hyphae 
Phacopsis is best developed in the lichen thallus, the algae are entirely absent- 
In other portions of the lichen thallus the algae are surrounded singly or in 
groups by the Phacopsis hyphae, the Evernia hyphae being absent from such 
places. In other places the hyphae of both Phacopsis and Evernia are found 
entwining the algae. Thus it appears that the Phacopsis hyphae in time 
‘reach the algae in limited areas of the lichen thallus and gradually displace 
the hyphae of the latter. It seems that the algae multiply more rapidly for 
a time after the Phacopsis hyphae reach them, but may finally disappear 
entirely where these hyphae are most abundantly developed. When the 
Phacopsis hyphae have reached the region of the lichen thallus where the 
algae are found, they spread laterally until large portions of the Evernia cortex 
are cut off from the medulla within and finally die. The Phacopsis hyphae 
are found to penetrate into the dead cortex and into the medulla of the Evernia. 
The foreign hyphae are absent from the spermagonia of the Evernia and areas 
immediately surrounding them, but are present in the soredia, which may 
serve as portals of entry. The conclusion is reached that the Phacopsis is 
probably first a parasymbiont and later a parasite on the lichen thallus 
Karschia destructans Tobler is described from the thallus of the lichen 
Chaenotheca chrysosephala (Turn.) Th. Fr. It was found that the Karschia 
penetrates into and through the crustose thallus of the Chaenotheca and into 
the bark upon which the lichen thalli examined grew. In growing through 
the lichen thallus, the Karschia is found to entwine and destroy algal cells 
and to displace and destroy the lichen hyphae. This makes the Karschia a 
parasymbiont with the lichen and likewise a parasite on it. But finally, the 
Karschia hyphae penetrate into the bark, after which ‘the fungus fructifies. 
So before the fungus produces its fruit, it becomes a saprophyte. Thus @ 
parasitic, a parasymbiotic, and a saprophytic condition are found in one 
ontogeny. The author reaches the conclusion that the Karschia is for a time 
a lichen-fungus (we would say a lichen), but at other times a parasite or 4 
saprophyte. Whether this fungus is a lichen is really a matter of definition ; 
but whether a given plant should be called a lichen or not is of no speci 
biological importance. If its relationship with the alga is accompanied by 
no morphological characters which should separate it from the genus Karschia, 
