This will be better understood by referring to the course pursued by these bodies generally. When the spore of a parasitic fungus settles on a plant, it frequently behaves as follows:--The spore germinates and forms a slender tube of delicate consistency, blunt at the end, and containing colourless protoplasm, as shown, highly magnified in Fig. 272, and in Figs. 273 and 274 much less magnified. De Bary long ago showed that such a tube--the germinal-hypha--only grows for a short time along the surface of the organ, and its tip soon bends down and enters the plant, either through one of the stomata or by boring its way directly through the cell-walls. Professor Ward says these phenomena suggested to himself that the end of the tube is attracted in some way, and by some force which brings its tip out of the previous direction, and De Bary has suggested that this attraction is due to some chemical substance excreted by the host plant. It is remarkable with what ease the tube penetrates the cell-walls, and which Ward believes to be due to the solvent action of an enzyme, capable of dissolving cellulose. “Miyoshi carried these observations a step further when, in 1894, he showed that if a leaf is injected with a substance such as ammonium-chloride, dextrine, or cane-sugar (all substances capable of exerting chemotropic attraction on fungus-hyphæ), and spores of a fungus which is _not parasitic_ are then sown on it, the hyphæ of the fungus penetrate the stomata and behave exactly as if the fungus were a true parasite.