Bui. 1038, U. S. Dept of Agriculture. 



PLATE VI. 



Vertical Sections of Pecan Leaves Killed with Carnovs Fluid. 



Fleming's triple stain used. A, C, and E toH, Van Deman variety. Collected in July, 1913, at 

 Belleview, Fla. A.— Section of healthy leaflet at the margin, showing well-defined palisade 

 and spongy parenchjona and large intercellular spaces. B.^Section of a yellow, thin area in 

 a large resetted leaflet, showing a differentiated palisade, but close packing of the cells. C. — 

 Section through the yellow area of a much-aborted leaflet where the tissues have partially col- 

 lapsed. There is no well-defined palisade tissue. D. — Section of a much-aborted leaflet at the 

 margin, showing the close packing of the cells. E and F.— Sections through the yellow, thin 

 portions of a badly mottled but nearly full-sized leaflet, showing the lack of differentiation 

 into palisade and spongy parenchyma, almost complete obliteration of intercellular spaces, and 

 difference in the leaf diameters in the center (F) and toward the margin (E) of a yellow spot. 

 G. — Normal leaflet, showing palisade cells well differentiated and typical loose arrangement of 

 the spongy parenchyma. H. — Section through the green tissue around a yellow spot of a 

 mottled leaflet, showing slight hypertrophy of the palisade and spongy parenchyma cells and 

 the reduction in size of the intercellular spaces in the spongy tissue. A to F, X 220; G and H, 

 X 420. Photomicrographs by the writer. 



