816 Transactions. — Botany. 



and vary in size throughout the secondary stems. In the 

 younger wood of the autumn specimens I found them occurring 

 very rarely for the space of two or three nodes, but after that 

 they appeared botla in pith and cortex, though few and irregular 

 in size. In the older wood much larger glands are found, but 

 these are also irregularly scattered, and usually among others 

 considerably less in size (fig. 7). They appear to develope very 

 late in the wood, and appear more frequently in the pith. The 

 contents of the glands of the specimens which had been pre- 

 served in alcohol had, as in the case of the leaves, coagulated 

 into little brownish-yellow masses, apparently of gum. 



My observations on the development of these glands were 

 imperfect, but they seem to point to a lysigenous origin, for the 

 following reasons : — When first the glands appear in the youug 

 leaf or stem, they appear as two or three colourless cells. These 

 cells increase in size, and appear to divide repeatedly, until they 

 form a mass of colourless cells of the size of the mature gland 

 (see fig. 8). [This is easily distinguishable fi-om a vein, as the 

 latter consists of an external bundle-sheath enclosing a bundle 

 of thick-walled cells, slightly pear-shaped with the pointed end 

 upwards, the whole being surrounded by chlorophyll cells (see 

 fig. 3) ] . The central cells of the colourless mass seem now to 

 become absorbed, leaving two or three rows of flattened cells 

 (colourless) on the outside, surrounding a vacuole with gummy 

 contents. In the glands of the stem I repeatedly noticed ragged 

 cells and portions of cell-walls projecting into the vacuole of the 

 gland, as if the interior cells had been partially absorbed but 

 the absorption had not been completed. Whether this absorp- 

 tion were partial or almost complete, the surrounding colourless 

 layers in the case of a full-sized gland always assumed a spherical 

 outline. 



EXPLANATION OF PLATE XX. 



Fig. 1. Transverse section through portion of mature leaf of Myoporum 

 Icetum X 160 : e, upper oiiidermis ; p.p, palisade parenchyma ; p, 

 spongy parenchyma ; .7, gland. 



Transverse section through portion of mature leaf preserved in 

 alcohol X 120. Letters as before. Gland shows gummy contents. 



Transverse section through portion of leaf showing vein (v) X 50. 

 The red substance above the vein is some apparently gummy 

 substance, which is very common in the leaves. 



Longitudinal section through midrib (slightly inclined), showing 

 gland (!j) X 1G6. 



Longitudinal section through young bud X 83, showing growing- 

 point, ().p. 



Longitudinal section through young bud X 83, showing young 



glands, g. 

 Transverse section through stem X 25 ; p, pith ; f.v.b, fibro 

 vascular bundles ; c, cortex ; g, glands. 



Transverse section through leaf X 83, showing young gland, g. 



