APIUM GRAVEOLENS 467 



compensate for the absence of an interfascicular cambium wliich, 

 when present, serves the purpose of adding secondary vascular 

 elements to the conducting system of an axis. Nestel (16) has 

 reported rare instances in which there were small isolated bundles 

 in the cortical parenchyma. These were amphicribral in contrast 

 with the amphivasal condition found in medullary bundles. 



Anatomy of the Petiole. — The petioles of the leaves of the 

 first year constitute the principal edible part of the plant, and the 

 marketability of celery depends upon their quality. Sayre (lo) 

 has pointed out that the desirable characteristics. are crispness, 

 tenderness, the absence of strings, and a pleasant, sweet, nut-like 

 flavor. Undesirable qualities which decrease marketability are 

 pithiness, toughness, stringiness, and a rank or pungent flavor. 



Several of these characters are definitely related to structure, 

 and this has focused attention upon the developmental anatomy 

 of the petiole. Norton (17) has stated that "Quality in celery 

 is primarily a question of the proportional relationships of the 

 so-called parenchymatous tissue to the fibrous tissue," and he 

 attributes the differences in quality, aside from those that are 

 hereditary, to external factors including soil moisture, plant food, 

 especially nitrates, rate of growth, light, and temperature. Mills 

 (14) regards high quality as being determined by flavor, which he 

 thinks is associated with the chlorophyll content in the stalks, 

 and by degree of crispness, which he relates to the water content 

 in the plant. He notes that lack of crispness may be the result of 

 excessive temperature, too much or too little moisture, nitrogen 

 deficiency, and excessive retardation or acceleration of the growth 

 rate. Like other investigators, he attributes part of the pithiness 

 to heredity, pointing out that some varieties of celery develop 

 this undesirable characteristic more frequently than others. 



Thompson (13) has noted that storage conditions may affect 

 crispness, especially insufficient moisture and too high temperature, 

 which result in over-rapid maturation and pithiness. Sayre (1.0) 

 investigated eight varieties of celery to determine the anatomical 

 factors which might have a bearing upon stringiness and tough- 

 ness, concluding that 



"The only celery tissue that seemed to have a very definite relation 

 to stringiness was the collenchyma," and "pithiness is evidently 

 correlated with a breaking down of the parenchyma cells which leaves 

 large open spaces through the center of the stalk." 



