ILLUSTRATIONS. 



Page 



Frontispiece. — Nine months old seedling almond showing large 



gall development at the crown I 



Fig. i. — Five-year-old almond tree in the Glendale orchard, show- 

 ing large galls almost completely surrounding the crown 

 a few inches below the surface 17 



Fig. 2. — Diagram showing almond seedlings growing under old dis- 

 eased trees in the Glendale orchard 20 



FlG. 3. — Diagram representing the number and position of diseased 

 and undiseased almond seedlings grown in the green- 

 house in 1897-189S 21 



Fig. 4. — Diseased almond seedlings resulting from inoculating soil 



with minced galls in 1897-1898 23 



Fig. 5. — Diseased almond seedling resulting from inoculating a 

 health}' seedling by making an incision through the 

 bark and inserting a bit of fresh gall tissue 24 



Fig. 6. — Diseased almond seedling showing two galls, both the re- 

 sult of making incisions through the bark and inserting 

 bits of gall tissue 24 



Fig. 7. — Almond seedling grown as a cutting in water culture, show- 

 ing a developing gall six weeks after inoculation 25 



Fig. S. — Almond seedlings from a single row, showing the relative 

 number of diseased to undiseased trees, in soil previously 

 inoculated with minced galls 27 



Fig. 9. — Diseased almond seedlings grown in pots of crushed quartz, 



in which were placed small pieces of the galls. ....... 2S 



FlG 10. — Characteristic galls produced on the roots of an almond 

 seedling by the action of the common gall-forming 

 nematode worm. 31 



FlG. 11. — Seedling almond, one-half natural size, showing a large 

 gall with small pustules of fresh, hypertrophied tissue 

 developing on its sin face 33 



Fig. 12. — The root and stem of an almond seedling, cut longitudi- 

 nally so as to show the gall attachment. 34 



FlG. 13. — A longitudinal section through the crown of an almond 

 seedling and attached gall, showing the darkened, dis- 

 colored outer portion of the gall tissue a short time after 

 growth had ceased . ... .... 35 



FlG. 14. — A portion of the stem of a seedling almond, twice natural 

 size, showing the returning hypertrophied tissue after 

 excision of the gall 35 



