FIRST REPORT OF OIL CAVITIES IN SCROPHULARIACEAE AND REINVESTIGATION OF AIR SPACES IN LEAVES OF LEUCOPHYLLUM-FRUTESCENS

Conspicuous air spaces in Leucophyllum (Scrophulariaceae; Leucophyllea e) leaves have been suggested to be developmentally transformed secret ory cavities. We reinvestigated air space development in Leucophyllum frutescens, using freehand sections of mature fresh leaves and paraffi n sections of several leaf stages. Each of the numerous air spaces per leaf forms because greater separation occurs within a local group of spongy mesophyll cells than in the developing spongy mesophyll elsewhe re. We found no anatomical evidence of transitory epithelial cells or lysis of cells in developing air spaces, thus the hypothesis that air spaces are transformed secretory cavities is not supported. However, a n important finding was that all leaves had one pair of conspicuous tr ue secretory cavities flanking the midvein at the apex, each lined by an epithelium and filled with oil. We also found conspicuous apical ca vities in freehand sections of herbarium specimens of this and three o ther Leucophyllum species. Cavities were not. seen in L. revolutum or in the related Eremogetan grandiflorus. This is the first report and d escription of a true internal secretory cavity in Scrophulariaceae. In the related family Myoporaceae, we found epithelium-lined cavities sc attered abundantly in leaves of cleared samples of three genera.