322 BOTANICAL GAZETTE [NOVEMBER 
of Dicranum, Bryum, Grimmia, or Fissidens with Cladonia, Physcia, 
or Amphiloma have been collected. The following species deter- 
minations of mosses based on vegetative characters may be taken 
as probable: Dicranum scoparium, Bryum caespiticium, B. argen- 
teum, Grimmia apocarpa, G. pennsylvanica, and Fissidens adian- 
toides. Especially important among the lichens concerned are 
Cladonia cristatella, C. baccillaris, C. pyxidata, Physcia stellaris, 
P. obscura, and, Amphiloma lanuginosum. 
All previous observations along this line are based on cultures 
and the examination of teased materials. The method employed 
consisted of imbedding and sectioning moss-lichen colonies, the 
resultant serial sections giving a veritable moving picture of the 
conditions in the colonies. The striking destruction of moss tissues 
is evident from sections 10 w or more in thickness, but to judge 
the extent and nature of the haustorial action it is necessary to 
have sections 3 uw or less in thickness. Many kinds of fixatives 
were used to show to the best advantage the various tissues con- 
cerned; no one fixative gave the most satisfactory fixation for all. 
The fungus elements of the lichen fix well in chromoacetic; the 
algal elements in hot bichloride of mercury. The location of the 
nucleus in the algal cells, and the condition of plastids in the moss 
show well in aceto-formalin. The cell wall structures of all the 
tissues showed best in aceto-formalin. Very weak Flemming’s 
solution gave excellent results in the young tissues of the moss. 
The three tissues, moss, fungus, and alga, can be sharply differ- 
entiated by a carefully balanced Flemming’s triple stain. For 
wall studies nothing proved better than a contrasting safranin- 
analin-blue stain. With this stain the cell wall changes and the 
haustorial action may be clearly demonstrated. Slides so stained 
were easily photographed by suitable combinations of yellow and 
green filters. In addition to the section studies, a long series of 
cultures was run with Amphiloma and other lichen genera to see 
how readily and under what conditions they would attack a moss 
host. 
The destructive action of lichens on moss may be seen from 
figs. 1 and 2. These were from to p sections of intimate mixtures 
of Cladonia lichens with Dicranum, Grimmia, and other mosses, 
