Leaf and Bud Initiation in the Gramineae

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Abstract
The rhizome and early aerial shoot of Agropyron repens possess short apices bearing only a few primordia, but become longer during the growing season and maintain more primordia in smaller steps in advancement. Later the apex elongates and becomes transformed into the inflorescence. The highest axillary buds to grow out, produce "blind" shoots. The shoot apex consists of 3 thimble-shaped layers[long dash]the dermatogen, the hypodermis and the subhypo-dermis, all referable to separate initials[long dash]enclosing a central core. Periclinal divisions in the dermatogen and hypodermis initiate the leaf primordia, lateral spreading of the divisions converting the original crescent into a collar which then grows upwards to give a miniature cowl inclosing the apex. The internal tissue of the young leaf is derived from both the dermatogen and the hypodermis but not the subhypo-dermis and core. Radial files of cells in the subhypodermis foreshadow the production of axillary buds but no peri-clinal divisions occur in either the dermatogen or the hypodermis at the position of the future bud tip. The subhypodermis and core of the bud are derived from the subhypodermis of the main axis. It is suggested that the zonation observed in the apex is not due to any particular qualities inherent in the cells themselves but to the particular types of metabolism in these strata, leading to a less rigid concept than that of either the Hanstein or the Breslau schools.