SCIENCE-GOSSIP. 



125 



plants do not require a period of rest during the 

 twenty-four hours of the day, but make increased 

 and vigorous progress if subjected during the day- 

 time to sunlight and during the night to electric 

 light. Working with a plant consisting of a vertical 

 dynamo machine, a regulator, a lamp, and a three- 

 horse Otto gas engine as motor, he found that the 

 electric light is both efficacious in producing 

 chlorophyll in the leaves of plants and in promoting 

 growth. He estimated that a light centre equal to 

 1,400 candles placed at a distance of six and a half 

 feet from growing plants appears to be equal in 

 effect to average daylight in February ; that, while 

 under the influence of electric light, plants can 

 sustain increased stove heat without collapsing — 

 a circumstance favourable to forcing by electric 

 light. 



D. Schi'ibeler, of Christiania, has also found that 

 when under the influence of continuous electric 

 light plants develop more brilliant flowers and 

 more aromatic fruit than when under the alter- 

 nating influence of light and darkness. With the 

 naked arc-light all observers agree that plants 

 present a withered appearance, but when a thin 

 piece of glass is intercepted between the arc and 

 the plant it absorbs the highly refrangible and 

 invisible rays of the arc which work destruction 

 on the vegetable cells, while it allows the luminous 

 rays of less refrangibility to stimulate their action. 

 Sir W. Siemens states that plants grown and 

 brought to maturity under the influence of con- 

 tinuous light will produce fruit capable of repro- 

 duction. 



Some interesting experiments were carried out by 



Professor L. H. Bailey, in America. He had two 

 greenhouses, one exposed to the li^ht of the sun by 

 day and kept in darkness in the night-time; the 

 other exposed to the sun's light by day but lit by 

 the arc-light by night. The effect of the naked 

 arc-light kept on .all night was to hasten the 

 maturity of the plants ; but it was found injurious 

 to them in the long run. The plants died when 

 they were kept in darkness during the daytime and 

 exposed to the electric arc during the night. Little 

 starch was found and no chlorophyll. Professor 

 Bailey insists on the danger of placing the plants 

 too near the arc-lamps, for it is apt to engender a 

 too rapid hastening to maturity. The period in the 

 development of the plant when it is most liable to 

 suffer from the electric-light is when the plantlet is 

 losing its support from the seed and is beginning to 

 shift for itself. Electricity, he asserts, has an 

 effect on the colours of flowers and fruit, some- 

 times a very disastrous effect. 



The conclusion arrived at from these experiments 

 is that electricity, if incautiously employed, may 

 prove an enemy to plant life rather than a friend. 

 What we want is more experiments. It would be 

 interesting, for instance, to know whether the 

 electric or magnesium light has any marked and 

 substantial effect on the actual germination of the 

 seed. Dr. Burdon Sanderson and others have 

 told us much about the role played by electricity 

 in the life of a plant ; but it is the practical 

 application of electricity to horticulture, which 

 is of most interest to market gardeners and 

 cultivators. 



80, Elsham Road, Kensington, II'. 



TRANSFORMATIONS TO PUPA. 

 By J. Herbert Allchin. 



HP HE changes which occur in the life of a butter- 

 fly are, owing to the rapidity with which they 

 take place, not very easy to observe unless the 

 student has the good fortune to possess a large 

 stock of spare time and a still larger fund of 

 patience, when he may, by maintaining a persistent 

 watch, be enabled to view some of the transfor- 

 mations. But as it is not many who can devote 

 the time necessary for that purpose, I think, perhaps, 

 the following notes — although the facts are not for 

 the first time observed — may interest some of the 

 readers of Science-Gossip. 



I have reared, at various times, many lepidopter- 

 ous larva;, but it was only last summer that I was 

 fortunate enough to witness the actual change 

 from the larval to the pupal condition, and a most 

 interesting sight it proved to be. 



Having in captivity a large number of larva; of 

 the small tortoiseshell butterfly (Vanessa urtica), 



when they showed signs of being ready to pupate I 

 seized every opportunity to have a look at them, 

 until at last I was rewarded by observing one just 

 as the change was commencing, and was thereby 

 enabled to make a few hasty sketches of the various 

 phases of the process. When I say that the entire 

 proceeding occupied but three or four minutes it 

 will be understood that the sketches were necessarily 

 of a very rough character, and that there was no 

 time to fill in much detail, but they are sufficient 

 to explain the creature's procedure. 



The first step the caterpillar takes to prepare .for 

 the coming change is to attach itself by the last 

 pair of claspers, or false legs, to a small tuft of 

 silk-like web, fixed on the under surface of some 

 convenient object, generally a leaf of the food 

 plant, which, in the case of Vanessa urtica, is the 

 common stinging nettle (Urtica dioica); thus it 

 hangs, head downwards, an apparently dead object, 



