46 PROCEEDINGS OF THE 



how the legumiuous phmts restored the soil, and no doubt there 

 is still much to be discovered regarding it. 



Virgil mentions the lupin as a field-crop, we only know it as a 

 flower grown for ornament ; but to the present day in Germany 

 lupins are grown very extensively on very poor soil every third 

 or fourth year, simply to be ploughed in to enrich the soil ; the 

 lupin is so bitter that no animal will eat it, but sometimes it is 

 used in Germany as bedding for the cattle. The lupin ILiqnnus 

 luteus, Linn.] thus grown has a yellow flower. 



February 19th, 1903. 



Some Eemarks on the possible Uses of Essential Oils in the 

 Economy of Plant-life. By Dr. Geokge Henderson, E.L.S. 



Everybody knows that moisture in the air tends to prevent 

 frost at night, but it is not always realized that the moist air, even 

 when clear and when there are no clouds, still acts in the same 

 way, and stops radiation from the surface of the ground. 



Professor Tyndall, thirty-two years ago, experimenting on this 

 subject (see his ' Fragments of Science '), found that infinitesimal 

 quantities of essential oils in the air enormously increased its 

 power of absorbing heat-rays of low tension. 



I am not aware that anyone has applied this fact as serving any 

 useful purpose in plant-life, but it seems to me that in this way 

 these oils may often prevent injury from frost at one of the most 

 critical periods of the plant's life, namely, Avhen it is setting its 

 fruit. 



In the low hills of the Punjab Himalaya, from 1000 to 4000 

 feet above the sea and 10 to 20 miles across, in the end of March 

 and in April, when most of the plants are coming into flower, the 

 blossoms are apt to be blighted by late frosts, at least one would 

 expect this ; but at that season the air is filled with the odours of 

 essential oils from these blossoms to such an extent as to be at 

 times (and especially on a still night, when frost most often occurs) 

 quite overpowering. 



My theory is that these essential oils help to prevent radiation 

 at night, and thus preserve the blossoms and allow the fruit to set ; 

 after all, it is usually only a matter of four or five degrees' fall of 

 temperatui'e just at sunrise which does all the damage. 



I mention the Punjab Himalayas because it was there the matter 

 first attracted my attention, and probably nowhere else is there 

 more risk of damage from late fi'osts. 



Tyndall states that, taking the absorptive power of dry air at 1, 

 moisture added to the air increases this power to 72 ; but an 

 infinitesimal trace of 



Oil of Eosemary gives 74 

 Oil of Laurel " „ 80 

 Camomile flowers ,, 87 

 Cassia „ 109 



Spikenard ,, 355 



Aniseed „ 372 



