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



PLATE XII. 



FRESH Living Cells of pecan Leaves. 



Camera-lucida drawings of freehand vertical sections, mounted in water. All at the same mag- 

 nification (X about 1,200) and oriented the same as in the leaf. A. — Health j^ paUsade cell, 

 showing well-deflued nucleus and plump livid-green chloroplasts. B. — A disorganization stage 

 of a palisade ceU in a leaf affected with rosette; chloroplasts disintegrated and nuclear outline 

 vague. C. — Healthy cell of the spongy parenchyma. D.— Slightly diseased cell of the spongy 

 parenchyma in which the chloroplasts have lost a part of their green color. E. — Spongy paren- 

 chyma cell at the margin of a yellow area. The protoplasmic structures on the side toward the 

 spot (right) are disorganized and the nucleus is fragmenting. Chloroplasts next to the green 

 periphery of the spot Ueft) are stiU green and unfragmented, though a part of them are smaller 

 than normal. F and G. — Spongy cells at further stages in disorganization. H. — Spongy cell 

 showing entire disorganization of contents. I. — Tannin degeneration products gathering into 

 flocules at a later stage of the disease in a spongy cell. J. — Spongy cell at the red-brown stage 

 with more or less homogeneous reddish brown contents plasmolized. K. — Spongy cell at the 

 margin of a yellow area (right) showing chloroplasts red-brown, but unfragmented on the side 

 toward the spot. This form of injury is rather uncommon. Drawings by the writer. 



