288 The Ohio Journal of Science [Vol. XVI, No. 7, 



27. Prillieux, E. Etude sur la Formation et le Developpement de quelques 



Galles. Ann. Sc. Nat. Bot. 3:113. 1876. 



28. Riley, C. V. Insects injurious to the Hackberrv. Part of 5th Rept. U. S. 



Ent. Comm. 601-622. 2 galls figured. 1890. 



29. Ross, H. Beitrage zur Kenntnis der Anatomie und Biologie deutscher Gall- 



bildungen, I. Ber. d. D. Bot. Ges. 28:228. 1910. 



30. Rubsaamen, Ew. H. Die Zoocecidien, durch Tiere erzeugte Pflanzengallen, 



Deutschlands und ihre Bewoliner. Lief. I. Stuttgart. 1911. 



31. Stewart, A. The Anatomy of the (Andricus) Punctatus Gall. Am. Jour. Bot. 



1:531-546. PL 2. 1914. 



32. Thomas, Fr. Zur Kenntnis der Milbengallen und Gallmilben usw. Zeitsch. 



f. d. ges. Naturwissensch. 42:513. 1873. 



33. Wells, B. W. A Survey of the Zoocecidia on Species of Hicoria caused by 



Parasites belonging to the Eriophyidae and tlie Itonididae (Cecidomyiidae) 

 Ohio Jour. Sci. 16:37-57. 2 pis. 1915. 



EXPLANATION OF PLATES. 

 (See also table of abbreviations following.) 



Plate XII. 



Fig. A. Cross section of normal one year old stem of Celtis occidentalis in winter 



condition. X 170. 

 Fig. B. Longitudinal section of one year old stem. X 170. 

 Fig. C. Section of normal leaf blade. X 180. 

 Fig. Ca. Study of leaf vein. X 190. 



Plate XIII. 



Fig. 1. Simple gall of Eriophyes sp. causing witches-broom, showing a common 

 mode of early development at one of the nodes. 1 yr. old. X 1. 



Fig. la. Longitudinal section through base of gall branch. X IJ^. 



Fig. lb. Sketch of 2 yr. old "broom" showing relation of secondary gall branches 

 to the primary ones. Tlie bark has been removed. X IH- 



Fig. Ic. Detail study of part indicated at c, Fig. la. X 120. 



Fig. Id. Study of trachea and adjoining cells indicated in Fig. Ic. X 400. 



Fig. 2. Sketch of smooth specimen of lepidopterous twig gall. X \]/2- 



Fig. 2a. Longitudinal section of gall shown in Fig. 2. X IH- 



Fig. 2b. Diagram of normal stem section (transverse). X 18. 



Fig. 2c. Diagram of gall section (transverse). X 18. 



Fig. 2d. Detail study part d, Fig. 2c. X 150. 



Fig. 3. Median section through gall of Pachypsylla vesiculum. (diagrammatic). 

 X 20. 



Fig. 3a. Detailed study of part indicated at a, Fig. 3. X 100. 



Plate XIV. 



Fig. 4. Gall of Pachyps^dla sp. on side of stem. See also PI. XIX, Fig 10. X 5. 



Fig. 4a. Diagram of cross section of gall and stem. X 22. 



Fig. 4b. Detail of part i), Fig. 4a. X 100. 



Fig. 4c. Detail of part c, Fig. 4a. X 100. 



Fig. 4d. Detail of part d, Fig. 4a. X 380. 



Fig. 5. Gall of Pachypsylla gemma. X 5. 



Fig. 5a. Diagram of transverse section of P. gemma. X 22. 



Fig. 5b. Detail of part b, Fig. 5a. X 150. 



Fig. 5c. Normal bud. X 5. 



