106 ^h' Gustav Mann on Fertilisation in [sess. li. 



and labellum, the hook-like process of the cokimn consists of 

 ordinary rounded parenchymatous cells, some of them con- 

 taining acicular crystals, and embedded in them are three tracts 

 of spiral vessels. The cells become smaller and smaller 

 towards the point of junction with the labellum, while the 

 epidermal cells also become smaller ; but they soon broaden 

 out again in the labellum, and some of them have protuberances 

 which further on get elongated, and the cells become stellate 

 as in the Eush (fig. 3). It is also possible, as Mr Scott Elliot 

 pointed out to me, to distinguish that the main axis of these 

 cells are arranged parallel to the long. axis of the labellum, 

 that is to say, that if we would draw lines through the main 

 axis of these cells, we would get lines radiating from a com- 

 mon point near the attachment of the column to the labellum. 

 From the main axis of these cells there are from three to five 

 projecting arms joining one cell with another. 



The epidermis of the labellum also exhibits a very 

 remarkable structure. The epidermal cells which are next 

 the column have a corrugated appearance, the highest point 

 of the cells being in the middle ; but as one travels towards 

 the apex, one finds the highest points of the cells becoming 

 shifted more and more forward, until in the region of the 

 larger yellow spot they come to form distinct bulgings point- 

 ing towards the apex of the labellum. 



In general appearance these cells (fig. 2) strongly resemble 

 those on the under surface of the lid of Ccphalotus, the cuticle 

 showing a striped appearance, the cells of one transverse row- 

 alternating with those of the next row. About the middle 

 of the labellum, however, these downward-directed bulgings 

 become less marked and less striped, while at the same time 

 peculiar pit-like depressions make their appearance; these pits 

 are directed upwards, and are formed in the following way : — 



The epidermal cells alternate as already stated; now we 

 liave, say, between two cells of the upper row a cell of the 

 lower row. The end of this cell, which is next the centre of 

 the flower, is' depressed or concave, while the other end pro- 

 jects slightly outwards, and is convex, forming the bulging, 

 but in a less marked degree. The two halves of the upper 

 cell roof over the concave depressed part of the lower cell, 

 and thus a pit is formed, with its cavity directed tow^ards 

 the centre of the llower. Sometimes, however, three upper 



