Chap. I. FOOD AND DIGESTION. 41 



worms had crawled, as was sliown 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 pre- 

 sented 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 broken 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 discoloured, and some of the 

 palisade and mesophyll cells contained 

 nothing but broken down granular matter. 

 These effects must be attributed to the trans- 

 udation of the secretion through the epidermis 

 into the cells. 



The secretion with which worms moisten 

 leaves likewise acts on the starch granules 

 within the cells. My son examined some 

 leaves of the ash and many of the lime, 

 which had fallen off the trees and had been 

 partly dragged into worm-burrows. It is 

 known that with fallen leaves the starch- 



