CELLS.— STARCH. 
33 
made to the recently prevalent and destructive epidemic 
among the Potatoes , which I believe to have been a 
disease of the tuber, not of the haulm or leaves. 
Examined in an early stage, such Potatoes are found to 
be composed of cells of the usual size, but they contain 
little or no starch ; and hence it may be inferred, that 
the natural nutriment of the plant being deficient, the 
haulm dies, the cells of the tuber soon turn black and 
decompose, and fungi are developed as on most other 
decaying vegetable substances. A portion of healthy 
Potato , shown in Fig. 21, consists of a series of more 
FIG. 21 . FIG. 22 . 
Portion of healthy Potato with starch Portion of diseased Potato showing 
grains in situ. absence of starch. 
or less hexagonal cells, full of granules of starch 
of different sizes ; the granules, when highly mag- 
nified, exhibiting the peculiar markings represented in 
Fig,. 19, d. 
In the diseased tuber, illustrated by Fig. 22, it will be 
noticed that the starch-grains are absent from nearly all 
the cells, their place being occupied by numerous minute 
D 
