12 



It has been stated that gardeners in the Azores have noticed 

 the deTelojDmeut of buds of roses to be quickened by the admission 

 of smoke into the conservatories. If this be so, one must suppose 

 that the smoke employed is wood smoke, consisting entirely of 

 particles of carbon or vegetable ash, and not the Impure smoke 

 which Avould be found in our conservatories, heated by coke or 

 coal. 



Thus far our observations i-efer to sun-light ; but perhaps the 

 most remarkable observations of the year are those made in deter- 

 mining the effect of the electrical light upon plants. For these we 

 are indebted to Dr. Siemens, F.R.S., who conducted his experi- 

 ments in this county near Tunbridge Wells. 



It is well known that chlorophyll (the green colouring matter 

 of leaves), starch, and cellulose, are developed in plants by the dis- 

 sociation of carbonic acid and water in the cells of leaves. The 

 power in nature which sets this decomposition in motion is sun- 

 light, and the question suggests itself, Is this power confined 

 entirely to sun-light? Sun-light contains «c/m/s/« ,- so does the 

 electric light ; and experiments show that the actinic rays in sun- 

 light play an important part in ripening grain and ftniit. Dr. 

 Siemens proposed to try whether a similar effect would be pi'oduced 

 by electric light, i.e., whether such light might be ad^-antageously 

 employed in aiding or supplementing sunshine in the growth of 

 plants, shrubs, fruits, and flowers. Our climate has not too many 

 hours of sunshine, and it would be a boon to the gardener to find 

 means of artificially gaining some of the benefits of sunshine. 



With a two-horse power engine and a dynamo-electric machine, 

 Dr. Siemens was able to produce a light equal to 1400 caudles. By 

 means of a reflector fixed in the open air, he directed this light 

 upon a sunk melon house. Pits were prepared with mustard, 

 cress, carrots, cucumbers, and melons ; and were di\ided into four 

 groups. 1 . Was kept entirely in the dark. 2. Was heated Mith 

 electric light exclusively. 3. Was exposed only to daylight. 4. 

 Had both dayhght and electric light, the latter from 5 to 11 p.m. 

 The results were : — 1 . Plants yellow, soon died. 2. Plants fight 

 green, pretty strong leaves. 3. Leaves of ordinary colour and 

 strength of daylight growth. 4. Plants had more strength, and the 

 gi-een was remarkably rich and dark. The next step was to place 

 the electric lamp in the same glass house with the plants. Here 



