1912] Morphology and Biology of Insect Galls 38 



be seen to have originated entirely from the cambium differ- 

 entiated by the producer of the galL Its irregularity on the 

 side opposite to the producer is very marked. X30. 



b'ig. 66. Aulacidea nabali Brodie on the stem of Prenanthes alba L. 

 Section through the stem of the host and the attached gall. 

 The relation of the cambium of the host to the cells of the gall 

 tissue is shown. X30, 



Plate XI. 



Fig. 67. Neuroterus majalis Bassett on the leaf of Quercus alba L. Sec- 

 tion through a larval chamber containing the pupa of the pro- 

 ducer. The dark band around the inside of the gall cavity con- 

 sists of the collapsed nutritive zone and the protective layer. 

 At the upper right of the figure the general nature of the cells 

 of the parenchyma zone is shown. X50. 



Fig. 68. Etiura S. gemma Walsh on Salix humiUs Marsh. Section through 

 a mature gall, showing a larval chamber containing a pupal 

 producer and several large masses of excrement. The general 

 nature of the small celled tissue of the gall is also shown. X30. 



Fig. 69. Euura (N.S.) on the leaf of Salix serissima Fernald. Trans- 

 verse section, showing one uninjured bundle of the petiole and 

 the parts of two others widely separated by the proliferation 

 of the tissue stimulated by the laceration of the bundles. X35. 



Fig. 70. Euura (N.S.) on the leaf of Salix serissima Fernald. Section 

 of a younger stage than the preceding, showing as before one 

 uninjured and two injured bundles. X35. 



Fig. 71. Euura ovum Walsh on the stem of Salix humilis Marsh. Trans- 

 verse section through the stem of the host and the gall originated 

 from it. It shows the wedge-shaped cavity occupied by the 

 gall mass and the origin of the latter from a cambium tissue at 

 the boundary of the pith of the host. X 18. 



Fig. 72. Euura (N.S.) on the leaf of Salix serissima Fernald. Section 

 of the gall showing proliferation induced by the excrement of a 

 larval producer. X 18. 



Plate XII. 



Fig. 73. Pontania hyalina Norton on the leaf of Salix alba L. Section 

 of gall with larva still within the egg membrane. Prolifera- 

 tion is shown well advanced in all the tissues of the leaf. X35. 



Fig. 74. Pontania hyalina Norton on Salix alba L. Section showing 

 the wound of the ovipositor. X25. 



