20G The Ohio Journal of Science [Vol. XVI, No. 7, 



heavily. The other cystolith just beyond the range of the gall 

 was entirely normal, the expanded part infiltrated with calcium 

 carbonate staining but slightly. Houard (10, [p. 109]) reports 

 aborted cystoliths on the border of a dipterous gall on Ficus. 



Among the largest cells found in any of the galls, were some 

 of the parenchyma units in the old, fully mature galls (PI. XV, 

 Fig. 6i). Contrasting with these are the normal cells of the 

 leaf mesophyll (Fig. 6k), those of the petiole before their walls 

 are thickened (Fig. 6m), those of the pith (Fig. 6n). All 

 were drawn to the same scale. 



The excessive enlargement of the gall cells can only go on 

 in those cells retaining thin walls. These cells, however, 

 cannot enlarge on the sides joining the lignified ones, hence 

 the expansion must be at the ends away from the sclerenchyma 

 cells. This type of development gives a characteristic radiate 

 structure to the parenchyma locally, where it surrounds isolated 

 sclerides or scleride groups, a condition presenting a striking 

 appearance in the section of the old galls. 



The discovery of the central, extremely narrow pit or 

 canal in the distal half of this gall, makes it possible to correlate 

 it to such varietal forms as Riley's P. curcurbita, which is 

 smaller and presents a prominent, wide, yet deep, apical pit. 

 If P. curcurbita should ultimately be shown to be a distinct 

 species, it would as such form a transition type between P. 

 vesiculum and P. mamma, though it stands closer to the latter 

 than the former. One P. mamma gall studied failed to exhibit 

 the presence of the distal pit. 



7. Pachypsylla venusta O. S. 



This gall is a large, hard, asymmetrical, pear-shaped modi- 

 fication of the petiole, variable in size according to the number 

 of chambers found in the gall; the chamber number being 

 directly related to the number of insects concerned in the 

 formation of one gall (PI. XIX, Fig. S; PI. XVI, Fig. 7). \-2}4 

 cm. long, S mm. -18 mm. wide. Surface minutely roughened, 

 destitute of hairs. Yellowish gray to brownish in color. At 

 one side, near the distal end of the gall is always a prominent 

 concavity which is apt to be bordered by the remnants of the 

 leaf blade. Interiorly, radiating from a central core, the walls 

 give rise to conic chambers (PI. XVI, Fig. 7a). This core, 

 however, is attached directly to the wall of the sunken area or 



