26

Aug 27 / 80

Ivy Leaf

Looked at the track with reflected light with 4 & 5 HK but 4 shows it best. It consists of a chain of irregular often star shaped dots * as shown in fig. 1; in some cases there were not so continuous as in this one.

In a good light I made certain that the surface of the epidermis is continuous & unaltered over the marks with 4 HK the normal parts of the leaf looks when seen from above by reflected light, like a collection of minute dark circles (fig. 2) with thick walls, the thick walls being the chlorophyll lining the palisade cells where the worm-marks are, these circles have thinner & vaguer walls, no doubt because of the destruction of the chlorophyll. This is shown in the centre of the dark patch in fig. 2. By transmitted light the worn-marks are almost invisible.

Little bits of leaf containing a line of marks were used for cutting transverse sections. In these sections places were found where a few of the palisade cells & some of the underlying mesophyll cells were injured.

They either contained nothing but granules or else chlorophyll grains which has lost all colour; & other paler. — Walls of cells not broken down —

This leaf was placed on pot with worms on Aug 22d & the worm mark was observed on 26th, & when then occurred worm had left bits of sand sticking on leaf, showing that worms had crawled over leaf.

* The transverse diameter of average stars was .2mm measured with eye piece micrometer.

(Back)

26v

These immense white marks covered whole surface of 2 leaves formerly placed on sand, but now worms apparently have found out that the leaves are too stiff to attack whilst fresh, for they visit them much less.

27

Aug 27

Ivy leaf (worms)

Fig 1 — HK 4 This is a sketch done quickly giving the general appearance, not an absolute copy

Fig 2 [sketch] rough sketch done from memory to show kind of appearance