1. Morphological characteristics: celery leaves are pinnate or deeply divided, with serrated edges, cylindrical corn stalks and textured surfaces.

2. Cell structure: By observing the shape, size and arrangement of sliced cells, it can be found that the cells of celery leaves are flat and loosely arranged, while the cells of corn stems are cylindrical and closely arranged.

3. Tissue structure: celery leaves are soft and rich in water, while corn stems are hard and rich in starch and cellulose.

4. Color: The color of celery leaves is dark green, while the color of corn stalks is light yellow.

5. Smell: The celery leaves are fragrant and the corn stalks have no obvious smell.

6. Taste: celery leaves have a soft taste, while corn stalks are tough.

Through the observation and comparison of the above aspects, the cross section of unlabeled celery leaves and corn stalks can be preliminarily distinguished.