314 Transactions. — Botany. 



Art. XXXVI. — Ohservatinns on the Glands in the Leaf and Stem 

 of Myoporum laetum, Forster. 



By Catherine Alexander, B.A. 

 [Read before the Wellington Philosophical Society, 10th September, 1886.] 



Plate XX. 



Distribution of genus. — The genus Myoporum is widely distri- 

 buted tbrougliout Australia and the Pacific Islands. The species 

 M. IcEtum 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 Koyal 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 schizogeuous origin, secreting passages, 

 epidermal or parenchymatous cells with mucilaginous cell-walls, 

 cells containing mucilage, raphides cells, cells with siugle 

 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. 

 Eound intercellular secreting spaces may be lysigenous, as in 

 Rutaccce, or schizogenous as in Hypcricinea-, 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 liutacecr, Myoporinece and Le- 

 guminosm ; schizogenous are constant in the Hypericineo', 

 Myrcinea, Sacwydea; and Myrtaccd." 



Also the following, from De Bary's " Comparative Anatomy 

 of the Phanerogams and Ferns," p. 202 : — 



"Ecsin, ethereal oil, emulsions of gum-resin of different 

 quality, according to the special case, and often little known as 

 regards chemical relations, occur : — 



• Vide Hooker's " N.Z. Flora," pp. 225 and 739. 



