28 BULLETIN 1038, U. S. DEPARTMENT OF AGRICULTURE. 
funet or bordering wounds where such tissues had fallen out, they 
presented a continuous, rough layer of glandular shields. Examina- 
tion of ordinary leaf wounds such as those made by insects showed 
no such abnormal development of resin glands. These conditions 
have been frequently observed in the general examination of leaves 
collected during several seasons and in different varieties and locali- 
ties. Furthermore, using a simple binocular microscope, observa- 
tions have been checked up by exact counts. For example, counts 
were made of the numbers occurring in a single field. in different 
parts of 10 normal leaves of the Frotscher variety collected at 
Thomasville, Ga. (1916), and in the yellow areas of 10 comparable 
rosetted leaves. The average for normal leaves was 8 to a field, 
while in the diseased leaves there were 92 to a field. In a lot of the 
Schley variety collected at Orangeburg. S. C. (1920), the average for 
healthy leaves was 43 and that for comparable yellow areas of 
diseased leaves 212 to a field. Similar results were found in material 
collected at Belleview, Fla., and at Baconton and Cairo. Ga. In some 
older spots of the secondary stage these resin glands were so closely 
packed together that counting was impossible. 
This increased development of resin glands is characteristic of 
many halophytes and xerophytes and in these cases apparently bears 
some relation to the condition of physiological dryness. Further- 
more, Tschirsch (80) has demonstrated that the secretion of resin 
is produced within the cell wall itself just below the cuticle. This 
region he calls the " resinogenous layer.'- Xutrient substances and 
water pass out of the protoplast into this resinogenous layer, to be 
there further molded into the final product, resin. This process, 
then, is participated in by both protoplast and cell wall and necessi- 
tates loss of material from both and a final breaking down of the 
cell wall itself. In pecan rosette this abnormal development of resin 
glands is then probably to be connected in some way with the gradual 
and general degeneration of the cells involved. 
In order to determine whether new spots may be formed after the 
full expansion of the leaf and whether yellow spots already formed 
may increase in size, resort was made to careful field observation and 
microscopical study of fresh living material. On July 20, 1920, at 
Orangeburg. S. C. the outlines of several hundred spots on 56 dif- 
ferent leaves of both primary and secondary stages were carefully 
traced with India ink on the upper surface of the blade. At the 
same time the outline of one leaflet on each leaf was traced on paper 
for comparison with its size at the end of the observational period. 
Furthermore, nonmottled areas of diseased leaves were marked in a 
similar way; and finally also certain areas of normal leaves were so 
marked as a check on possible injury by the India ink. These leaves 
were located on one normal and five rosetted trees in a 45 -acre 
