44 



THE ORCHID WORLD. 



[Xo\ember, 1914. 



Whenever the temperature is lessened there 

 IS a corresponding release of moisture in the 

 atmosphere, resulting in dew being formed 

 on almost every jiart of the roof and other 

 positions, from whence it falls in continuous 

 drops. We thus see how important it is to 

 diminish this atmospheric moisture whenever 

 there are signs of approaching cold weather. 



DENDROBIUM CRASSINODE. 



THLS Dendrobium was gathered by 

 Colonel Benson, in i8()(S, on the 

 mountains of Arracan, 150 miles east 

 from Moulmein, at 2,500 feet elevation, and 

 sent by him to the Royal Gardens, at Kew, 

 and to Messrs. Veitch, of Chelsea, in both of 

 which establishments it flowered simul- 

 taneously in January of the following year. 

 It was, however, known to science ten years 

 earlier, the Rev. C. Parish having sent a 

 sketch of it to Sir W. J. Hooker, at Kew, from 

 materials procured in the Siamese province 

 of Kiong-koung. It its native haunts it is 

 often found growing on the tops of the 

 highest trees, and in that position is difficult 

 to collect. 



Our illustration shows a handsome plant 

 flowering in the Royal Gardens, Kew. The 

 flowers are white, heavily tipped with mau\'e- 

 purple ; the labellum is pubescent on the 

 upper surface and minutely ciliated at the 

 margin, with a large yellow disc surrounded 

 with white, the apical margin mauve-purple. 

 The specific name refers to the swollen joints, 

 and the flowering season is from January to 

 March. 



In the variety albiflorum the flowers are 

 white, except the orange-yellow disc on the 

 lip. In the variety Barberianum the flowers 

 are of brighter colours than in the typical 

 form, while the mauve-purple blotches are 

 larger. Both these varieties were first intro- 

 duced from Burmah by Messrs. Low and Co., 

 and subsequently by Messrs. Veitch from 

 localities remote from that in which Col. 

 Benson's plants were obtained, whence it is 

 certain that this species has a considerable 

 range in the eastern peninsula of India. 



THERMOMETERS. 



WITH the rapid extension of horticul- 

 ture in all parts of the world, and 

 more especially by reason of the 

 close manner in which cultivators of Orchids 

 are brought together, it becomes necessary to 

 possess a good knowledge of the two 

 important methods of measuring temperature. 

 The following considerations should have 

 weight m favour of the adoption of the 

 Centigrade thermometric scale in horticul- 

 tural practice in place of the Fahrenheit scale. 



The temperature of crystallisation, or the 

 freezing point as it is familiarly called, if the 

 water be kept under the same pressure is 

 constant ; the normal pressure of the 

 atmosphere at sea-level when the barometric 

 column is 30 inches is about 15 lbs. to the 

 square inch. The temperature of conden- 

 sation from the state of steam, in common 

 parlance the boiling point, is also constant as 

 long as the pressure remains the same. 

 There are thence two invariable standard 

 points of temperature. 



On the thermometric scale the space 

 between the freezing and boiling points was 

 divided by Celsius into 1 00 equal parts, whence 

 this scale has obtained the name of the 

 Centigrade ; it is now generally in use on the 

 Continent and almost universally in scientific 

 investigations. On Fahrenheit's thermometer, 

 the instrument in common use in England, 

 the freezing point is marked 32 degrees on 

 an old assumption that the greatest terrestrial 

 cold was zero, an assumption that has long 

 since been proved in various ways and places 

 to be fallacious ; the boiling point is 

 212 degrees, the interval between the two 

 being 180 degrees, so that 5 degrees Centi- 

 grade is equal to 9 degrees Fahrenheit. 



The division of the interval between the 

 two invariable points into 100 parts is itself 

 so suggestive and simple both in theory and 

 practice as to require no justification. On 

 the other hand, as already shown, the placing 

 of the freezing point at 32 degrees is quite 

 arbitrary, and the division of the interval 

 between the freezing and boiling points into 

 180 units is equally arbitrary, and so far as 



