Dixon — On the Vegetative Organs of Vanda teres. 449 



distinction to those which morphologically belong to the cortex, which 

 he calls " Phloeoterma." The chains of cells containing the silicious 

 bodies appear to belong to the cortex. 



Leaves. 



The laminae of the leaves of V. teres are almost cylindrical, their 

 cross-section is oval, and they taper ofP to a fine poiat. On the 

 upper side there is a slight groove, which is evidently homologous 

 to the Y-shaped upper surface of other members of the genus, e.g. 

 V. suavis. This groov e disappears at the extreme apex and base 

 of the lamina. In a transverse section of a leaf anywhere about the 

 middle of its length, we see this groove situated at one extremity 

 of the long diameter (PL xiv., fig. 24). The large bundles of the leaf, 

 about nine in number, lie in the form of a U round the central part 

 of the leaf, with the largest, the mediam, bundle forming the lowest 

 part of the U. The smaller bundles are arranged outside these, and 

 more or less regularly alternating with them. If we trace these 

 bundles down into the petiole we find that as they approach the place 

 of union of lamina and petiole, which is marked by an absciss layer 

 and an annular groove round the leaf, they bend and pass into the 

 petiole with such a curvature that they maintain a tolerably equal 

 spacing from one another throughout their whole course. In some 

 cases fusions occur between the bundles shortly after they pass from 

 the lamina to the petiole ; in other cases a single bundle, when traced 

 downwards, is seen to divide into two, and persist as two, for the rest 

 of its course to the stem (PL xiv., cf. figs. 24 to 29). 



But, in spite of these variations in the behaviour of the bundles of 

 individual leaves, whatever happens to the bundles on one side of any 

 petiole {i.e. right and left of the midrib), is also found with wonder- 

 ful regularity on the other side, so that transverse sections of the 

 lamina and petiole are beautifully symmetrical. The small bundles 

 which connect two bundles with one another are also usually sym- 

 metrical on both sides of the leaf. Besides these connections and 

 fusions, which vary from one leaf to another, there are also fusions 

 which appear to hold good for every leaf. The small bundles which 

 run along close to the groove (representing the upper surface) of the 

 lamina as they pass into the petiole run along its oblique upper limit, 

 and passing round in it meet at the opposite side of the stem. At 

 this position they fuse together and form one bundle for the rest of 

 their course. This bundle passes down till it runs into a bundle 

 formed in a similar way from the two bundles next beneath these two, 



K.I.A. PEOC, SEE. in., VOL. m. 2H 



