THE STEM OF A SPECIES OF CUCURBIT. 197 
This epidermis does not line the central hollow, as would per- 
haps be expected. Instead of that, the central cavity becomes 
filled up, and a new cavity is formed which is surrounded by this 
internal epidermis. 
As to the physiological significance of the structure, further 
investigation will be necessary before anything can be said. 
In conclusion, [| should like to express my sincerest thanks to 
Professor Bayley Balfour, under whom these observations were 
made, and to Mr. W. Edgar Evans, B.Sc., who prepared the 
microphotographs, 
