U. \V. KING ON THE PHVSIULOGV OF MONSTEKA DtlJCloSA. 129 



which is raised horizontally and at a right angle to the petiole 

 by means of the petiole at the point of attachment to the leaf, 

 becoming flattened and corrugated, so that the corrugations can 

 fold back upon one another on the upper and stretch on the 

 under side, forming, as it were, a stop hinge, thus enabling 

 the blade of the leaf to rise and, spreading, perform its 

 functions. The cells across the joint approach to a hexa- 

 gon in transverse section, but as they recede from it 

 they become more cylindrical. Similar protuberances are 

 developed on the convex side of the petiole to those found on 

 the stem, but none are formed upon the concavity of the 

 petiole that sheltered the lamina. A longitudinal section of 

 the petiole shows a series of oblong cylindrical cells, the outer 

 layer coming in contact with the cellular prominences. Many 

 of the oblong cells contain clusters of square-shaped raphides, 

 but these are most numerous in the small hexagonal cells in 

 the node. Passing at intervals between the oblong cells are 

 large fibre cells and bands of needle-shaped raphides. Spiral 

 vessels, consisting of four to five united threads, course along 

 at intervals in the parenchyma structure, surrounded by bands 

 of small woody fibre cells. Laticiferous tissue is sparingly 

 distributed along the stalk. The general structure of the 

 petiole is (including the spiral vessels and raphides) continued 

 through the mid-rib and smaller veins of the lamina. The 

 epidermis of the latter consists of five to six-sided cells, cover- 

 ing loosely-arranged parenchyma ; that, with numerous inter- 

 cellular spaces in it, forms the substance of the leaf. Stomates are 

 distributed over its under-surface, but none exist upon the 

 upper surface away from the veins, upon which a few are to be 

 found. The stomates are formed of two kidney-shaped cells, 

 whose concave sides are opposed to_^one another, and the cells 

 surrounding them are irregularly six-sided. The limiting cells 

 of the membrane of the apertures in the leaf become thickened 

 similar to the cells forming the limit of the growth of the 

 edge of the leaf. These apertures or perforations are a part 

 of the organization of the plant, gradually moulded from the 

 germ, as any other organ of the plant is, and in a measure 

 essential to the life of the plant. They are an advantage to the 

 plant by allowing the moisture and rain to drip through the 

 apertures to the roots growing beneath them, or the roots 



