Organization and Significance of Lenticels in Dicotyledons. I. Lenticels in Relation to Aggregate and Compound Storage Rays in Woody Stems. Lenticels and Roots

1. Lenticels may with advantage be considered transverse or longitudinal, in accordance with the orientation of the fissure. 2. The orientation of the cauline lenticel is clearly correlated with the nature of storage ray within. 3. Forms with aggregate storage rays of primitive nature in the stem, that is, composed largely of congeries of uniseriate rays, possess transverse lenticels. In contrast, these species in which the storage aggregations consist of multiseriate units, for the most part, are found to have longitudinal lenticels. In the latter cases the pericycle usually shows a disruption under the lenticular organs. Alnus, Corylus, and Carpinus typify this condition. 4. Forms with compound storage rays in the stem at maturity, but in which the compounding is completed only after many years, possess the more primitive lenticels, the transverse type. Those species in which the storage ray becomes compound within a very short time, one to three years, are found to have confronting each ray one or many longitudinal lenticels. These may even be so closely approximated as to appear as a single greatly elongated structure. Quercus offers the only example found of this situation. 5. Roots, irrespective of internal conditions and taxonomic affinities of the species concerned, all show paired appendage lenticels, the primitive type found to be characteristic of young coniferous stems and all coniferous roots, indicating the conservative nature of the root. 6. The intimate relation between the type of storage ray and the form of lenticel facilitates a satisfactory aeration of the living tissues within the stele, with the consequent maximum metabolic activity.