PLATE 4 
Photomicrographs of pectic granules in the middle lamellae and of crowngall bacteria 
in the intercellular spaces of gall tissue 
A. 1 —Four-day-old gall. Pectic granules (a) are visible in the middle lamellae 
between large cortical cells. They have been observed in rapidly growing uninocu¬ 
lated tissue in July. Free-hand section, unstained. X6oo. 
B. —As A, except taken from an uninoculated plant grown in the greenhouse. X 634. 
C. —Eight-day-old gall. The intercellular spaces (a) are filled with bacteria and 
surrounded by newly formed regions of hyperplasia (b) and hypertrophy (c). The 
region containing bacteria is enlarged in figure D. Paraffin section stained with 
dilute carbol-fuchsin and light green. X200. 
D. —An enlargement of the region containing bacteria in figure C. The intercel¬ 
lular spaces which contain the bacteria are maked a. In the slide these walls and the 
bacteria are stained red while the rest of the tissue shown appears green. X634. 
1 A and B were photographed in March, 1922. 
