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are to function. Under proper conditions, the spore germinates and a new 
mycelium develops in the wood. The steps in the decay-processes from 
the time of infection to the production of the mature fruiting body differs 
with the species of polypore concerned and somewhat also with the kind 
of tree affected. In the case of the fungi which attack the woody parts of 
trees, delignification of the cell-walls usually takes place, at least the lignin- 
cellulose composition of the cell-wall is destroyed. It is supposed that 
an enzyme similar to hadromase, isolated by Czapek, is excreted by all 
wood-rotting fungi. The products of the activities of cytolytic enzvmes 
then, form the main food for the fungus. Many other compounds, such as 
tanorins and proteids, are used by some of the wood-rotting fungi. 
Saprogenesis. The majority of the polypores may live purely as 
saprophytes. Some do so more commonly than others. However, 
this saprophytic habit is only incidental, since it does not form a required 
phase in the life-history which produces anything that is not produced in 
the pathogenic phase. The same kind of inoculum, however, is formed in 
saprogenesis as in pathogenesis and this may initiate new primary cycles. 
Pathological Histology. To illustrate the process by which the my- 
celium of wood-rotting polypores causes the decay of the wood, prepared 
cross-sections and longitudinal sections of beech wood, rotted by Fomes 
pinicola (Swartz) Fr., are provided. The sections are stained to show; 
lignified cell-walls, light green (methyl green); delignified cell-walls or 
cellulose, brownish red (congo red); and middle lamella, light red (ruthen- 
jum red). OBSERVE :— 
11. The abundant and light-colored hyphae of the fungus in the 
partially decayed wood. pDRaw. 
12. The large dark-colored hyphae where new tissue is being 
delignified. DRaw. 
13. The delignification of the wood-elements. Which layer of 
the cell-wall is delignified first ’ 
14. The characters of sound beech wood, elements present, 
and thickness of walls of different elements. 
Make a DRAWING of healthy beech wood at a point showing both 
spring and summer wood with all the elements properly arranged and 
detailed. Label fully. 
15. The characters of the decaved wood, noting the changes 
brought about in the elements. ] 
Make a DRAWING of decayed beech wood showing the same elements 
as in the drawing of healthy wood. Label fully, and bring out all the 
‘changes caused during the decay-process. If necessary, make DRAWINGS 
of the intermediate steps between the healthy and decayed wood, using 
the cell-wall of a single element to illustrate the point. 
REPORT 
1. Hand in report-sheets filled out giving your determimation 
of the family and genus of each of the numbered specimens. 
2. Hand in the notes taken on the named specimens and an 
original dichotomous key (arranged like the one in the outline) by which 
each species can be determined. 
