148 Miscellaneous. 



The marginal glands which form the fringes of the leaf have a 

 very different form from those of the surface. In the marginal 

 glands, the substance of the })edicel seems to expand at the apex into 

 an elegant oblong cup, at the bottom of which the carmine-coloured 

 glandular tissue is spread. The central glands on the contrary are 

 simple papillae of a more or less rounded, ovoid or elliptical form, the 

 outer ones being of a more or less red tint, whilst those nearest to 

 the middle of the limb are colourless. 



The structure both of the central and marginal glands is very re- 

 markable, for it is not merely a single spiral vessel that exists in the 

 gland, but a voluminous group of large reticulated cells occupies the 

 centre of the organ. These reticulated cells have expanded meshes 

 in the colourless central glands of the leaf, but the meshes of those 

 nearest the margin are narrow. The middle of the marginal glands 

 is also occupied by a considerable group of similar cells. 



The pedicels of the marginal glands are dilated at the base and of 

 a green colour ; they become insensibly narrower, their green colour 

 becomes paler and passes to rose in the upper part which supports 

 the gland, which is elongated and attenuated at the base. These 

 pedicels are composed of an epidermis, a coloured parenchyma, and 

 a vascular system. 1. The epidermis is formed of long cells, which 

 become shorter from the base of the pedicel to its apex ; they are 

 colourless at the base of the organ, tinged with rose colour at its 

 upper part. In many cases the epidermic, or rather superficial 

 utricles, were furnished with grains of chlorophyll on the wall con- 

 tiguous to the green parenchyma : this is a fact to which I would 

 call the attention of anatomists. Some small stomata are most fre- 

 quently scattered between the epidermic cells towards the dilated 

 base of the pedicel, and some may even be found at a considerable 

 height upon it. There are also some small eminences, or short, 

 simple or bifurcated hairs, scattered on its surface. 2. The green 

 parenchyma is also composed of elongated cells, which contain a pro- 

 portion of chlorophyll equal to that of the tissue of the leaf itself. 

 This parenchyma goes on diminishing with the diameter of the 

 pedicel, so that towards the top it only consists of one or two series 

 of cells surrounding the vascular axis ; the green matter also dimi- 

 nishes in the interior of the cells, and at last is even sometimes 

 replaced by the rose colour. 3. The vascular system is usually com- 

 posed of single central bundles, but towards the base of the pedicel 

 there are sometimes two bundles distant from each other which unite 

 higher up. Each bundle is composed of two or three tracheae of 

 great delicacy, often having two spiral fibres at a little distance and 

 turning in the same direction. 



This is the structure of the pedicels of the marginal glands. If we 

 examine that of the glands themselves, from their posterior to their 

 anterior face, that is to say, from the surface corresponding with the 

 lower surface of the leaf to that which corresponds with the upper, we 

 find the elements arranged in the following manner. First, there is 

 an epidermis of colourless or rose-coloured cells, then a layer of cells 



