78 
logical units. In regard to the lower lichens and some of the 
higher (Nostoc-bearing) there seems to be evident semi-individual- 
ism, though further carefully conducted experiments are necessary 
to settle this point. 
Without entering into details I shall briefly summarize the es- 
sential differences between lichens and the ascomycetous fungi. 
This summary is deduced from. the.results, obtained by the most 
scientific lichenologists during the past forty or fifty years. These 
statements are especially intended for those who are continually 
forgetting that there is a difference between fungi and lichens. 
1. The morphological adaptions of the vegetative portion of 
lichens is primarily for the furtherance of the function of ch/oro- 
phyll-assimilation ; in fungi it is for the furtherance of the function 
of reproduction (distribution of spores, etc.). 
2. Fungi are essentially parasitic and saprophytic. Lichens 
have partially or wholly lost the saprophytic or parasitic function 
and have phylogenetically acquired the power of converting inor- 
ganic substances into organic compounds by a process of photo- 
synthesis. Morphologically and physiologically lichens resemble 
other chlorophyll-bearing plants; fungi do not. 
3. In lichens the mechanical tissues * are specially adapted to 
support: and»protect the .assimilation tissue; in fungi the mechan-' 
ical tissue is specially adapted to support and protect the sporoge- 
nous tissue. 
4. The soredia of lichens are special phylogenetically-derived 
propagative organs and have no homologues among the fungi. 
The cyphellae and cephalodia are also phylogenetically derived 
lichen-structures. 
5. The spores of fungi can develop into mature fungi; the 
spores of lichens cannot develop into mature lichens. In other 
words fungi may develop from spores, lichens cannot. 
6. Lichens are better adapted to resist extremes of tempera- 
ture and dryness. Fungi are better adapted to dark moist places. 
7. In general lichens are long-lived while fungi are short-lived. 
Some of the higher as well as the lower lichens (C/adonia, Par- 
— 
* More fully described by Zukal and in my Text-book of General Lichenology 
now in press. In this book the citations of the more important literature on lichen- 
ology will be given. 
