Anatomy of the Vegetative Organs of the Pineapple Ananas comosus (L.) Merr.-Concluded. III. The Root and the Cork

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Abstract
All roots in the older pineapple plant are of adventitious origin. These do not originate in a pericycle but are formed in a zone restricted to a short vertical distance, in the comparatively young apical portion of the stem. The root is initiated partly in the (meristematic) dictyogenous layer which lies at the boundary between the differentiating cortex and stele, and partly in the innermost layers of the cortex of the stem. The structure of that portion of the root within the stem and that external to the stem differ; in the external portion an exodermis is present and rap-hide-bearing cells are found in the outer cortex. The vessels are formed very close behind the region of ro6t histogens which makes the pineapple root unusual, as far as the literature shows. Cork is the only secondary tissue occurring in the pineapple plant. It is of the "storied cork" type and is of non-phellogen origin.