Page:Transactions NZ Institute Volume 19.djvu/382

. XXXVI.—Observations on the Glands in the Leaf and Stem of Myoporum lætum, Forster.

By, B.A.

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Plate XX.

Distribution of genus.—The genus Myoporum is widely distributed throughout Australia and the Pacific Islands. The species M. lætum is common in the North and South Islands of New Zealand on the sea coasts as far south as Otago. It is also found in the Kermadec Islands (M'Gillivray), and Chatham Islands (W. Travers).

Description of the leaves.—One character of the whole genus is the occurrence of pellucid glands in the leaves. The mature leaf is 2–4 inches long, lanceolate or obovate-lanceolate, acute or acuminate, serrulate above the middle, narrowed into petioles, bright-green and lucid.

Glands in leaves.—The following I extract from the "Journal of the Royal Microscopical Society," October, 1884, page 769:—

"The various causes of transparent dots or lines in leaves are:—Secreting cells, round intercellular secreting spaces of either lysigenous or schizogenous origin, secreting passages, epidermal or parenchymatous cells with mucilaginous cell-walls, cells containing mucilage, raphides cells, cells with single crystals or clusters of crystals, cystoliths, spicular cells, branched sclerenchymatous bundles, groups of sclerenchymatous cells, depressed pits with or without hairs, crevices in the tissue, stomata. The secreting cells, spaces, or passages may contain resin, gum-resin, balsam, or an essential oil. Secreting cells are an extremely common cause of transparent dots, and are usually characteristic of whole families, or at least genera. Round intercellular secreting spaces may be lysigenous, as in Rutaceæ, or schizogenous as in Hypericineæ, the two kinds showing no difference in the mature condition. Both kinds are of great importance from a systematic point of view, furnishing distinguishing characters for entire families. Thus, lysigenous secreting spaces occur in the Rutaceæ, Myoporineæ and Leguminosæ; schizogenous are constant in the Hypericineæ, Myrcineæ, Sacmydeæ and Myrtaceæ."

Also the following, from De Bary's "Comparative Anatomy of the Phanerogams and Ferns," p. 202:—

"Resin, ethereal oil, emulsions of gum-resin of different quality, according to the special case, and often little known as regards chemical relations, occur:—