. Bulletin. 1901-13. Agriculture; Agriculture. i U) Fig. 7.—Enlarged section of lower (spore-bearing) part of fig. 6. HOW FUNGI AND BACTERIA GROW. The fmigi and bacteria that destro}^ wood obtain their food by breakinof x^p tlie complex chemical comi^ounds of which wood is com- posed into simpler substances, utilizing some of these and leaving some either as gases or solids. A crude idea of the working of a fungus may be obtained by comparing it to a Avheat plant. The wheat plant takes something from the soil and something from the air. After it has taken these substances from the soil and air
. Bulletin. 1901-13. Agriculture; Agriculture. i U) Fig. 7.—Enlarged section of lower (spore-bearing) part of fig. 6. HOW FUNGI AND BACTERIA GROW. The fmigi and bacteria that destro}^ wood obtain their food by breakinof x^p tlie complex chemical comi^ounds of which wood is com- posed into simpler substances, utilizing some of these and leaving some either as gases or solids. A crude idea of the working of a fungus may be obtained by comparing it to a Avheat plant. The wheat plant takes something from the soil and something from the air. After it has taken these substances from the soil and air they are changed. When the wheat i)lant has accumulated enough food it forms seeds. Just so the fungus. It takes all of its food from the wood, and leaves a different substance, rotted wood, behind. When ready it forms a seed i)lant, the j)unk or toadstool. It obtains its food by giving off peculiar liquids, known as ferments or enzymes, which have the power of transforming wood fiber into substances which the fun- gus uses for food. Their action usually results in whole or partial solution of the substance attacked. Sugars and starches are attacked bj' different ferments; the sugars may be absorbed by the fungus directly, or changed to some more easily digested sugar. The starches are changed to sugar and are then absorbed. The nitrogenous substances undergo similar changes. Wood fiber may be dissolved entirely by the ferments, or only the cellulose or lignin elements. Some mycelia excrete fer- ments which attack only cellulose, others only the lignin, while others attack starches and sugars. When one part of the wood substance is removed it is no longer wood. The chemical changes have brought about j^rofound j)liysical changes. The hard, elastic Avood fibers have become a soft mushy mass, or a drj^, brittle substance which falls to pieces at the slightest touch. Figures 9-11 show a number of structural changes in the cell walls. At first the liypha? simply puncture tlie ce
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