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Show 40 IIAJ3lTS OF WORMS. CnAP. I. rest of the leaf was fresh and green. Several leaves of lime and elm removed from burrows out of doors were found affected in different degrees. The first change appears. to be that the veins becmne of a dull reddish-orange. rrhe cells with chlorophyll next lose more or less completely their green colour, and their contents finally become brown. The parts thus affected often appeared almost black by reflected light; but when viewed as a transparent object under the mic:oscope, minu~ specks of light were transmitted, and th1s was not the case with the unaffected parts of the same leaves. These eiJ'ects, however, merely show that the secreted fluid is highly injurious or poisonous to leaves; for ·nearly the same effects were produced in from one to tw.o days on various kinds of young leaves, not only by artificial pancreatic fluid, prepared with or without thymol, but quickly by a solution of thymol by itself. On one occasion leaves of Corylus were much discoloured by being kept for eighteen hours in pancreatic fluid, without any thymol. With young and tender leaves imn1ersion in human saliva during rather warm weather, acted in CHAP. I. FOOD AND DIGES'riON. 41 the same manner as the pancreatic fluid, but not so quickly. The leaves in all these cases often became infiltrated with the fluid. Large leaves from an ivy plant growing on a wall vvere so tough that they could not be gua wed by worms, but after four days they were affected in a peculiar manner by the secretion poured out of their mouths. The upper surfaces of the leaves, over which the worms had crawled, as was shown by the dirt left on them, were marked in sinuous lines, by either a continuous or broken chain of whitish and often star-shaped dots, about 2 mm. in diameter. The appearance thus presented was curiously like that of a leaf, into which the larva of some minute insect had burrowed. But my son Francis, after making and examining sections, could nowhere find that the cell-walls had been Lroken down or that the epidermis had been penetrated. When the section passed through the whitish dots, the grains of chlorophyll were seen to be more or less djscoloured, and some of the palisade and mesophyll cells contained nothing but broken down granular matter. These effects must be attributed to the trans- |